My question for you is, what type of riding do you do? If you do a lot of higher speed runs and track days, go for the r6. If you do a lot of street riding, the cbr 600rr or the gsxr is the way to go, if you do a little of both, zx6r. The r6 has horrible low end power (ie makes it harder to ride in the city in stop and go traffic) and has a very aggresive stance. Gsxrs have great ergos and are probably the most comfortable. Cbr's are probably the slowest of the 600's, but the ergos are great on them, mid range is amazing, and cbr's are bulletproof reliable. a lot of people say the cbr is the "easiest" to ride. I just picked up my 2012 zx6r the other day so I can't really chime in how much I like it since I've only ridden it a few times, but i will say it has pretty good low end power and the ergos are tolerable (I do find my wrists being sore after a ride though) Hope this helps.