There is no wrong choice here. Even though it sounds like the OP has made a decision, I'll add some RC51 specific info for thread readers.
I've owned twins and 600s and litres. I owned an 00 RC51 (first year) back in the day from brand new. I recently bought an 04 RC51 SP2. Anyone who thinks the RC doesn't handle well can't ride imo. The bike is no light weight and thus ponderous at low speed, but it handles great beyond single digit speeds on the street and on the track. Stable yet still quick steering and confidence inspiring. The first bike I put my knee down on, at both the street and the track.
I recommend going for the SP2 as there were a lot of improvements. Especially if you are going to push the bike at the track. The SP1 overall chassis was too stiff and at the limit the feel becomes a little vague and traction suffered as well. The AMA and WSB RC51's had these changes, and the chassis changes showed up on the SP2. Here is a little discussion of frame design challenges.
http://motodna.com.au/flex-or-not-flex/
All RC51's were geared quite high, much more for a large track than the street. With a gearing fix it becomes much livelier on the street. The RC51 will do a 10.55 second 1/4 mile with better gearing (ref'd from article discussed below). So while not litre bike quick, it isn't that far off. There are also some other minor mods that people do.
This article sums up the bike well.
Honda RC51 - Great sport bikes of the past. http://www.sportrider.com/features/146_0908_honda_rc51_rvt1000r_sportbike/viewall.html
I like litre bikes a lot. Litre bikes were my traditional favourite, but now with the unforgiving and draconian ON legislation it is hard to really enjoy what advantages they bring to the table. Heck, even twisting the wrist on an RC51 for a few seconds can get one into a lot of trouble.
On the streets of ON, a v-twin sportbike is plenty fast, it won't egg you on like a I4 to rev it out and potentially get arrested, and for booting around the powerband and character make it more enjoyable. A well set up RC51 has lots of torque, great handling, and a lot of character. With decent exhaust, the v-twin sound will get a lot of attention. And the gear driven cams add a whine to the mix for additional mystique.