So I've got myself in something of a situation. I find that I'm spending an increasing amount of time in the company of another who is not a gamer. In a world where everyone's something of a gamer, even if it's just a game of Farmville at lunchtime, or some Bejeweled on the mobile phone, this new friend plays none at all. We do not have this in common.
Balancing three distinct factions in a competitive multiplayer game is one of the tougher challenges in game design. (Just ask Blizzard, which has seen StarCraft's tenth anniversary come and go before it's managed to nail down the second outing for the Terrans, Protoss and Zerg.) Three is too few to allow for variations on a theme; in such intimate company, each faction is going to have to stand out as an individual in the whole, not just in the detail. Each needs to present a completely rounded, completely unique play style.
Call it Freudian if you like, but I'm a bit of a wet lettuce when it comes to chitinous murder-beasts that impregnate people with their foul spawn, and an ill-advised trip to the Trocadero's Alien War at the tender age of 13 did nothing to endear me to Geiger's scampering Xenomorphs.