I had my GSXR 750 before buying my SD. I racked up quite a few miles on it road and track. I installed Helibars on it early on and at my height of riding it, could do 400 mile days (slab and twisties) without feeling it the next day.
Before buying my SD, I test rode an RC8 (not R). I'd read all the hype about what a comfortable RR it was. I call BS. After 20 min, I wanted my GSXR back. It might be heresy to say on this site, but the GSXR 750 does everything better than the standard RC8. The GSXR is faster, handles better, and rides better (street or track) and doesn't cook your legs in traffic like the RC8. Dump the extra money you'll spend on the RC8 on Ohlins 30mm fork cartridges and a TTX shock and OMFG - the bike is a weapon.
So why the eff am I on the SD.net board spouting the virtues of a GSXR 750? Because the SD is by FAR a better street bike IMO. The riding position is more comfortable than any SS - even my GSXR with Helibars. Its easier to maneuver in the city and while splitting traffic. It's not as top heavy as a SS so its easier to ride at parking lot speeds. (It doesn't want to suddenly take a nap on its side as you roll up to the gas pump. During my test ride, the guy in front of me dumped the other RC8 test bike in the parking lot. ) It's far more nimble. You can put it anywhere in the lane and carve through or adjust mid corner without major issues. Yes, fighting the wind blast on the freeway isn't fun, but that is the big trade off. The other trade off is that it won't hit 170 mph.
If I want to go fast (>120 mph) I'll grab the GSXR. Its easier to deal with at speed. (The fairings make it easier to move around on the bike at speed.) The GSXR has become my track bike. But, for most road work, the SD gets the nod. I suspect that if you had the two, you'd gravitate toward the same conclusion. Flame on. (Its OK. I have my Nomex suit handy).
Edit: FWIW, I don't think either bike is the perfect compromise. I'm still looking for that bike. Let me know if you find it.