A teenage old man said:
Zerg because you can technically have over two hundred units without cheating, and you can have your eggs ready to hatch as reinforcements. The Terran are the worst units in the history of RTS's and the only strategy I ever use with the Protoss is: build a bunch of carriers, build a bunch of interceptors, attack enemies, which gets boring even though it always works. The Zerg offer many different strategies, most of which work out.
Easily countered with .5 Defiler/Carrier and by always having a nice satchel of Scourge behind the front lines (which you should ALWAYS have in case of Capital Ships entering the fray.)
I hate how people think that Carriers are the greatest thing ever... they're so easily destroyed as long as you know the basics of microing...
With the Terran, all you need is a Science Vessel with EMP Shockwave and a squad of Wraiths trained on the Carrier; Bam, you just wiped out half a squad of Carriers for half the price of what your foe paid.
IN OTHER NEWS
Anyone wantin' to play a game? I'm itchin' to get back in.