Wow, how long has it been since I've played a proper Planetstorm game on a 4'x6' table or bigger? At least fifteen years? Maybe more?
So with that disclaimer, here's what I sort of remember about Fantasia, all of which could be wrong. They have two huge weaknesses: their armor and their high rate of fire. High rate of fire weapons, like AK's and Flechette guns, are actually worse in Planetstorm than they are underground. That's because Planetstorm has a "pinning" rule, where if you roll the exact number required you "pin" your target instead of killing it. Statistically, high rate of fire weapons make up for a high kill number with extra dice. But the "pin" rule really penalizes them. A RAM Laser being able to kill on a 5+ at medium range is fine. It can kill or pin. But a AK with a kill on a 6+, even with two dice, means the best you can do is pin. Meanwhile, at those ranges the Fantasians are vulnerable because their armor is so bad. While they can only pin someone at medium range, incoming fire can effectively kill them on a 4 or 5 and pin on a 6.
What I remember is that the Fantasian Katyusha batteries help make up for those deficiencies. They can just sit back behind cover and rain death (or the equivelant, EMP death), forcing your opponent to come to you into short range. In instances where you have objectives, so you can't just sit and wait, the Fantasian's superior speed keeps them competitive.
But really, to be competitive with the Fantasians, you need a Katyusha battery (3 T-34's armed with the rocket launchers).
I also seem to remember their MASLAW shoulder mounts were really good, better than the TOW. I don't remember the stats, but I think what made them better was you could choose whether to use them in an anti-armor or anti-personel role.
Didn't they also have a sniper who was really cool? Hm, I'm gonna have to dig out planetstorm and refresh my memory.