I rode 2 different 600RRs and I personally think they were both extrememly slow. They had no torque or power up to 9k at all. My old 2002 Kawi ZX6R felt a lot better. Hell my roomates old carb'd R6 felt stronger.
Ive never rode a 636 before but I imagine that would be the better 600cc choice for the little extra power on the street. Nothing like being able to crack the gas a bit to get out of the way when a car comes in your lane