H'm, I more or less followed the writers, they were very clear on the UNE WW2 references, but I never picked Infranites for Elves. Back in the day I played Infranites and Eldar, though, so that's SPOOKY.
I loved and still love the Infranite sculpts. The BAP lacks some refinement (underbelly!) but IMO looks better than most competitors even today. The Lightning makes Eldar jetbikes embarrassing to have ever bought. The Infranite scouts are still one of the most dynamic power-armoured miniatures in existence. In game, ironically, I haven't played the Infranites much, I tend to end up playing UNE. That's probably because I'm paying Defiance in lieu of Planetstorm, it's even more figure-hungry and UNE are easier to get! I need more Infranite models, BTW.
I love the UNE concepts but the sculpts are a bit variable (the NCO with his enormous arm, the Carl-G gunner with his even more enormous arm). The concepts though were still kicking other company's tails ten years later, particularly the Heavy Assault Troopers and Assault Support Platform. The ASP might be the only power-armour in any game to come close to Starship Troopers levels of firepower. I still need more UNE models.
In terms of concepts, I liked that the Black Empire was quite alien, but still dignified. The Storm Angel is a great idea! Amazons in Power Armour with Laser Swords riding CYBER RAPTORS! How did you guys not get rich with that? I don't own any BE miniatures, but if they were back in production I would.
Machines. I like 'em. Their specialised, unbreakable troops are awesome. Lots of variety and a complete line including vehicles! I statted up the Dreadbot for Defiance and it's a MONSTER of limited-ammo rocket-powered destruction.
Fantasians I have no experience of but their big support armour looked retro-soviet awesome IMO.