What do you think is worse? Comparing them myself, Text Chat is annoying as hell in games where you need to see. Such as Warcraft >_>
People will make accounts, join games, and make annoying names such as llllIIII1111llllIIII111, except Warcraft's text makes it look like llllllllllllllllllllllllllllllllll, so you can't use the mute command. Then, when the game starts, they hold down @ for a while, copy/paste that, and take up your entire screen with @.
Then, Voice Chat, you have mic spamming, idiots that suck at the game displaying their idiocy over chat, etc.
My vote goes to text chat, seeing as you don't need to use a mic, but I've never seen a text-chat that you could turn off.
Either one is annoying, but the latter is dead in FPSs, mostly because of type-kills.
Muting individual players should become a standard in all online games with voice chat.