It seems I've posted about this a lot, but...

I vastly prefer a smaller frame, basically the smallest frame I can fit on. Why? For starters, my size. I am 6'1" with a longish torso and long arms. On top of that, I do a lot of long steep climbs, followed by fast descents. I like to have my bar low enough that my back is flat when I'm in the drops and about 30 degrees when I'm on the hoods. I find that position helps a lot when climbing and on the flats. For descending, I like to tuck and get into a downhill skier position. So, it goes without saying that that is important, too.