Go with the 675. Smaller bikes make you a better, smoother rider. Bigger hp bikes hide mistakes much better.
To go fast on smaller bikes you have to brake later, carry more corner speed, get on the gas sooner!
The choice is yours of course. Personally I enjoy going fast on smaller bikes. I dont know how to explain it. I get more enjoyment out of actually having to work to go fast. Later braking more corner speed and going from braking to the apex then grabbing a wrist full of throttle is more work than "gas....break....turn....gas" . Ive ran 3 different bikes in many different classes throughout my club days. At one point I ran in 7 sprint races on Sundays using three different bikes. A 2004 zx 10... 2006 yamaha R6 and A old 1999 suzuki sv 650 that I ran in lightweight twins and in heavyweight twins. The sv was so much fun. I was winning in lightweight and coming in second place in the heavyweight class only to a damn Ducati 1098 with my lil ol sv. That bike made my lap times on the other two drop by seconds. Learning how to ride a small bike fast will only make you a better rider overall. It was so much fun beating big twins on the breaks and checking out on the lil ol sv.
I did run a 2007 gsxr 750 for about half a season. That was fun as well running it against the liter bikes. On smaller tracks where the straight speed really doesn't matter the lap times were just as good as most and better than some liter bikes. I ran faster lap times on my 750 than I did on that zx10. I just couldn't get on the gas as quick with the big bike. Times have changed and now there is this lil thing called traction control. Ive never been on the track with traction control. Im from the throttle control school. I would like to give it a try one day though. Might just be fun but whats the fun in letting the bike do all the work for you.
If you're experienced trackday user, F3 800 is the way to go.
Has the best of both worlds, supersport 600 agility with modern high rev wide powerband engine and with real world power output that you can actually use it.
Thanks guys. I went with the 675 and can't wait to get it on the track. I just need race glass, GP shift rear sets and a steering damper for now. Would love the gubellini setup in the future. Would love to hear some feedback on track set ups. Thanks again for the great advice.
I've had the time to ride both bikes hard and it's a toss up. 800 has better brakes and the slipper helps with control entering and exiting turns. The 675...well after the newest reflash...is just as intoxicating to wind up coming out of a corner.
It's a hard call to make but if you're buying new the extra power of the 800 will be good to have and there are other small things around the bike that are an improvement.