Not a question of which is better - it's a question of which you prefer, which fits your particular throwing style. I happen to prefer the Buzzz, but that's just me - it works for me. Others like the Roc - when in doubt, try both and see which you like.
They're both great discs! Buzz holds a line better for me, where the Roc flips a little more. But I guess it all depends on weight, wear stage, and the thrower. I throw the Buzz but I also carry a Roc, just in case I decide to launch mass midrange at a basket!