Tzeentch we can believe in. Chaos 2016.
In terms of choosing sides, I've been to many places before settling on Tau - sort of. Tau is the largest army I have for 40K. I think I have something like 1500 points worth of them. I also have 500 points of Black Templars lying around, 500 points of Grey Knights, 500 points of Dark Eldar ... if we go even further back, I also have a few units of Blood Angels.
The Tau just appeal to me because they're, like I think I mentioned earlier, the only ones who seem to actually care about tactics. I mean, sure, taking the shortest way toward the enemy is technically a tactic, but Tau are the only ones who employ any kind of sophisticated tactics. The Imperial Guard do it on some level, I suppose. But Tau are the only ones who actually designate targets for other units, support other units, that sort of thing. They're portrayed as a very dynamic combined arms force, who don't rely on ( or can call on ) limitless numbers of soldiers, or who fight to the last man rather than rethink their strategy. Also, drones. Drones are the fricking future, man. I'm thinking of having a very strong drone presence in my current army, just because FRICKING DRONES. Unfortunately, the really cool drones are from Forgeworld, which kinda sucks. Still, I'm almost tempted to getting bombers just so I can get Interceptor drones, because what can possibly be cooler than FRICKING DRONES detatching to intercept enemies? Nothing, that's what!
Unfortunately, fighters may be better overall. Quad Ion Cannon looks tasty for strafing the enemy, and I like the idea of dominating the airspace. Just as long as my enemy doesn't have similar plans, it should be cool...