675 any day of the week. Judging by your choice I would say you're leaning towards 2co or 13S R6? Far too peaky for the road, virtually no useable power. The 675 however is a blinding machine, and more than capable on track too. Plus that triple soundtrack and the raw induction noise is reason in itself! No brainer!
On a side note, glad to see this thread is still going! (I used to use this forum ages ago, but I can't access my old account.
Think I had my Telefonica K2 GSXR600 when I last posted! I lived in Oz and had a J1 ZX6R, K1 750 (Yoshimura EVERYTHING), a couple of dirt bikes (YZ125/250) and then came back, bought my old Telefonica back and then sold it in 2013. Had a E46 BMW for winter, then bought a CB500 (right laugh, upset all my friends on 600 sport bikes in the lanes) and a K1 GSXR1000 which I still currently have! Spent a fortune on it, Brembo MC, 5VY R1 monobloc brakes, K4 1000 forks, Power Commander and Quickshifter, TRE, Akrapovic system to name a few bits. Love the thing! She moves so well for an old bus; I most of 2014 upsetting trackday 'heroes' on sorted S1K's that they couldn't ride them.
Yet still, I find myself looking to sell it and get something like a 675, which shows how good they really are! Knew that story was relevant somehow.
Sorry for the life story, figured I'd make a post worth posting on this limited count!