See, here's my point...
ANY MONKEY CAN DRIVE A STRAIGHT LINE...
I ride with guys on 954 Hondas, a Gix 1000, an RC51, a TL1000R, and then a bunch of guys on 600's... and three of the five fastest guys are us on 600's... I have NO problem keeping up with the big bore bikes on most roads AT ALL... in fact, three of us on the 600's probably rule most of the twisty stuff... and it's hard to be left WAY behind on the straights too unless you don't gear it right or anticipate the straights. If you're going to cruise along at 5,000 rpm, you don't stand a chance, and in which case you shouldn't be riding a 600. We're talking a fraction of a second difference in the 1/4 miles boys, and if you're a good rider, you can EASILY make up for a slight roll-on power deficit in the corners. You'll be able to go in AND come out of corners faster, NO QUESTION in my mind.
Learn to ride the bike to the best of your ability. There is no replacement for RIDING ABILITY, forget about displacement and take advantage of the things 600's do MUCH better.
"Keep yer feet on the pegs and your right hand cranked."