The Roc has been an extension of my left hand on the DG course for years...and when I have a little room to the left of my target to play with (LHBH player), I can launch it out there up to around 250-260 feet, have it pause for just a split second, then gently glide down to the right at the target.
The Buzzz is faster and seems to hold a lower, straighter line...which I love, because I feel like I can rely on it more on tunnel/alley shots. However, I haven't quite been able to throw it as far as my Roc, except for in the Pro-D plastic.
I guess if I were forced to choose between the two, I would probably take the Buzzz, because I have other discs in my bag I can get to do what my Rocs do (though not as reliably)...while I don't have any other discs in my bag that can consistently hold those low, straight mid-range/approach lines like my Buzzz Pro-D and Elite-X plastic. Pains me to say that though, as Rocs are very close to my heart on the course.
Buzz without a doubt. It is one of only two Discraft discs in my bag along with the soft Magnet. It will do what you want when you want it. I just got one of those new RW Pro Rocs and it does not compare with my Buzz!