I always used to notice this weird thing in both Macross and Robotech fandom: the consistent off-the-cuff assumption that female Zentradi (or "Zentraedi") are a higher quality of soldier and personage than the Zentradi men. Nothing in any Macross material states this, so it's "fanon" in the truest sense, meaning fans coming together and agreeing upon some truth that they all perceive in the material, but that is not actually an official part of the universe.
I can think of a few reasons why this perception took root, but none of these reasons are enough for me to declare it a canonical "truth", or even something that aligns with my own interpretations of the series. This is true for Macross or Robotech, though only Macross' material holds weight. The Robotech-exclusive material can be studied more as a reaction to the original Macross, than something equal with it.
(Oh, and I'll add "Meltrandi" here to get search results, but I pointedly don't call female Zentradi "Meltrandi" because they don't need a special term, and it's used very rarely in media outside of DYRL, whose portrayal of Zentradi I hate anyway.)
The first reason that female Zentradi might be considered a better breed is that all of them are beautiful. The only"unconventional" female Zentradi design is the very muscular but otherwise pretty Veffidas Feaze of Macross 7. Any other female Zentradi are generically gorgeous according to the standards of modern culture, with the only thing odd about them being anime hair. Male Zentradi designs, on the other hand, run the gamut from the ugly to the handsome, with weird skin colours and the occasional cybernetic attachment.
As time goes on, the design gulf between the genders grows wider. The film Do You Remember Love? added giant brains to male Zentradi advisors and more extensive cybernetic attachments, and hinted that all male Zentradi soldiers were now bald. Not all of this was carried through to the main continuity, but much of it was, so that we have male Zentradi who still look like normal humans, but other characters with a more intense variety of "ugly" designs. The female designs, however, remain unchanged across all continuities.
There is also the question of whether the male Zentradi's goofy anime faces are meant to represent actual physical deformity, with buggy eyes, saggy skin, and apelike features. I don't think they were, though the Robotech novels certainly thought so. However, even if it's not deformity, it still represents the greater range of character designs among male Zentradi.
I'd argue that nobody on the creative ever intended that female Zentradi were literally more beautiful than male Zentradi, were be manufactured to be exactly that. Rather, it's just that old thing where male characters can have a wide variety of body types, while female characters must all be generically sexy. It's not actually part of the characters' biology, but just a motif that's used without thinking. In this case, I think fanboy-pleasing is part of the intention, but other than that, there is no deeper explanation for why female Zentradi are always "hot".
And viewers should never underestimate the power of beauty. Female Zentradi could be assumed to be of a higher class, more refined, intelligent, and elegant, simply because none of them are ugly or goofy-looking. My reaction is sort of the opposite—having a wider variety of character designs makes the male characters more interesting and engaging, while the more uniform female designs are duller.
It's also harder to call a group flawed when they have little screen time. While beautiful female Zentradi might make for popular characters, in the original series only Milia (Miriya) and Laplamiz (Azonia) had any substantial role, and only a small number of female soldiers and staff had any lines at all.
And even though Laplamiz exists, Milia Fallyna is undoubtedly more prominent. As usual, whenever a character is the major representative of their group in a series, he or she starts to define the series' representation of that group. Milia, who is beautiful, skilled, and whose comical moments are minimal, therefore becomes what viewers think all female Zentradi are like, because we see little to contradict that. And so the logic goes, if female Zentradi are all close in quality to Milia, of course they are superior to the men. In other words, because SDFM has a smaller amount of female Zentradi in speaking roles, it's easier to base the faction off of what we do see, than to assume it is diverse.
But to me, having less female Zentradi characters makes their faction less interesting, not more. I just can't imagine the entire faction being like Milia, every soldier only a little bit shy of being an "ace". Why would that be true of any army, even a fictional one? There have to be female equivalents to the Regult pilots that die like flies, Zentradi women who simply weren't fast or smart enough.
Regardless, I sometimes wonder if female Zentradi are given prominent roles in later stories, exactly because Milia was so popular. This is especially true if you include characters of mixed Zentradi/human race, but even so, most of the major Zentradi characters following Space War 1 have been female: Klan Klang, Veffidas Feaze, and the returning Milia. Likely this is just due to following what worked with the audience before, but I can see how this might contribute to a greater perception of the "worthiness" of female Zentradi to the fanbase, if the female Zentradi characters keep being the primary ones.
Male Zentradi also have many types of mecha, while female Zentradi have only one: the Queadluun-Rau battle suit. The Queadluun-Rau is one of my favourites, a big, bulky machine that's a far cry from the sleek and sexy armour I expected. Other people seem to agree with me, as the Queadluun is a popular choice for mecha art and kitbashing.
However, there's when the only female mecha is this wonderful, powerful death machine, it brings up the reputation of the female fleet. While the male fleet has smaller, more disposable mecha, such as the "legendary" Regults/Battlepods that get destroyed by the boatload, if the cool Q-Raus are all you have, it makes the female fleet look cooler by comparison. We all know there are female Zentradi soldiers dying left and right in the actual battles, but Queadluuns just look better than those fragile walking eggs, and the former might overwhelm the latter truth.
(I've also wondered if writers were less comfortable with using female characters as disposable infantry, and that is why female Zentradi don't do ground warfare. The only exception is the "Draug", a female Zentradi ground vehicle found in the PC game Macross VOXP, and its obscurity might still prove the above point. Also, it looks like a squished Queadluun rather than having a unique design.)
Notably, the upgraded mecha that cracked the "mainstream" of Macross are the Queadlunn variants: the Queadluun-Rae (or Rare) from Macross Frontier, and the Queadluun-Quilqua from Macross 7: The Galaxy is Calling Me. Sure, there are many upgraded versions of male Zentradi mecha, but they are confined to games and guidebooks, while anime releases are the backbone of Macross media. Furthermore, the Queadluun-Rae had several toys made of it, strengthening its representation. The accidental implication is that female Zentradi mecha reflect the supposed quality of their owners, both of being more worthy of being perpetuated and upgraded than their male equivalents.
Once again, though, my reaction is to prefer a range of things than just one "cool thing". I love the Queadluun-Raus, but was disappointed to understand it was the only mecha that female Zentradi had (despite those mysterious Regults in the belly of Laplamiz' ship, which have to be a continuity error). More is better, a wider range of things is more appealing.
I realize that no one takes stock in Robotech these days, but to make a point, I'll say that the Robotech expanded universe has its fair share of material that could promote this view of female Zentradi as superior. However, in this case this material is, if not strictly "fanon", still the result of people not involved in the original production looking at the material and drawing their own conclusions.
Every new female Zentradi created for this side of the Pacific is still good-looking (and usually has a name that sounds feminine to English-speakers, for some reason), and are more prominent than any new male characters created, with the most important ones being Seloy Deparra and Kazianna Hesh. All of them are Queadluun pilots, or in this case, the messy Romanization of "Quadronos", but given that their army was made of little else, I can let that slide. However, the focus on only creating new female characters for prominent roles might suggest a greater perception of "worthiness", the same way that most prominent new Zentradi in Macross are women as well, especially if we include those of mixed race. It's an odd coincidence.
In the original Palladium Robotech RPG, the only character class that a female Zentradi can have is "officer", while the male classes include the ranks of Officers of the High Command, Fighter Pilots, Officers, and Foot Soldiers. That makes so little sense: if they are all officers, who the hell do they have authority over? The exact reason for this choice is never given, but to me it seems like they thought a female Zentradi army would be more glamorous and didn't think about anything else.
Furthermore, when James Luceno wrote the midquel Robotech novels, he decided to chronicle the pointless and contradictory self-destruction of the Zentradi race. Stupid, but he also made a point of saying that the female Zentradi lasted longer, and that their deaths involved a last-ditch attempt to protect the earth. The choice of which gender to survive longer could have been random, but given what else we've seen, Luceno may have been another one of those who thought that female Zentradi were just better.
Newer Robotech material just doesn't deal with Zentradi because of the legal trouble surrounding Macross, but the newer version of the Palladium RPG does something very strange. You see, the Robotech dub made a few mistakes and had male voices among the female Zentradi one-offs, and the RPG tried to explain it by saying male Zentradi were assigned to "menial duties" among the female fleets.
This defeats the entire plot point that Zentradi were sexually segregated, which was a major component of their character arc. Besides that huge error, though, it might suggest that Palladium has bought into the fanon hype, because female Zentradi are just too cool and glamorous to concern themselves with the menial day-to-day running of a ship.
All of this is based on guesswork, since no one, to my knowledge, has ever actually said why they believe female Zentradi are of a higher calibre. Looking at what we're presented, I see plenty that would trigger that perception, but no real evidence for it. Furthermore, it helps me understand why, even though I'm a female Zentradi fan, the actual female Zentradi characters never interested me that much. It's because there are less of them in speaking roles in Super Dimension Fortress Macross, and in that group, a narrower range of designs and roles. What seems to make some fans think they're of a greater quality are the same traits that make me disinterested. Which is a shame.