Except I pretty much only play Aeon, so I really have no basis for comparison.
You can at least comment on #4 which units are more fun, and maybe #2 if you remember who you got started with Aeon.
I got started with Aeon because I'm a monarchist and like monarchy esque stuff, and I like religious zealots and fervor, same reason I go Vanu in PlanetSide 2. And I recently learned they are probably the most morally justified belligerents of the war, sitting idly by until the eldar were exterminated. Sorry I mean the 6 winged angels or whatever.
TBH I played for like 10 years just against AI, and IIRC in vanilla the Galactic Colossus had the most HP or otherwise felt like it had so much HP it was a walking game ender, an unstoppable being come to purge the world with holy atomic fire. But I've learned a lot about the game since then so IDK if that was true. Also their T3 fighter had AOE (or said it was flak) and that was baller.
Other than that I'm not quite sure. I play them now and appreciate their focused and specialized units, high alpha damage (though I also enjoy countering that with t1 scouts, milking overkill). The units fill a requisite micro level that I think is ok, though I am the man who thinks hover bombing is the devil and would automate tactical elements given the opportunity. I think some of the downsides are the more specialized units that are SO specialized they hardly see use, mercies, shards, and to a lesser extent Swifties and restorers. I also think some units are very specialized but should maybe specialize harder and require additional units for different niches. But that's changing the game, which isn't the point here.
I think Aeon fail to be noobie friendly because humans are weak spirited and not ready for the enlightenment of THE WAY.
Or it's because they require the slightest bit of thought to utilize effectively. I don't mean that degradingly. I mean that if you are new to the game, plop into a skirmish with AI and aren't some RTS savant, you get some resources, and start making stuff, then send it to attack. UEF and Cyb you can get pretty far just making their t1 attack unit and going in. Make Aeon tanks and send them in and they get slaughtered. Yeah you need radar, radar? What the fuck is radar? What are these grey blips? Anyway my tanks were shredded asunder so I'm going to make these cheaper and faster Flares now, clearly that's the intended T1 attacking unit, robots are cool. Maybe that tank is meant for a water thing? I see they can go on water, must be some special shit. Whats this, an OBLIVION cannon? Oblivion was trash so shooting it out of a cannon is alright. ooooOooaHHHH PEEEEWWWMMMMM, god DAMN that was awesome, did you see that it all charged up and shot this massive explodey thing, awesome! Oh it was killed by T1 stuff? What's that? Build T1 PD next to it for support and to mitigate it's shortcomings? Nono, 2 is higher than 1 so the T2 one is better, guess this faction just sucks.
Noobies are noobish when they come in, they are gonna look at everything though such a noobie lens. So yeah that's how I played against AI for 10 years and entered FAF ladder spamming LABS. Gee, wonder why I'm still 800 rank.