QUOTE (jcat @ Mar 10 2010, 09:03 AM)

if you actually look at the spec sheets, the liter bike just has some more torque and a little more top end power. Top speed is the same, liter bike is a bit heavier normally (though not necessarily the case anymore).
For the price difference, I'd stick with a 600. Or, if you want a bit more torque a 750 is a decent idea. I've always thought if I were to get a bike it'd be a k6/7 750.
Depends on what you are referring to, on older bikes yes this would have applied a bit better. On newer bikes this comes nowhere near close to being the truth. My bike weighs 10 pounds less than an 05 600RR has about 60 more hp and a bit more torque. Put that on paper and tell me how much of a difference their is.
To answer the original question it all really depends on what you like and how much self control you have. I went from a carb'd ZX7 to a cammed Busa, to a ZX14 which could have wiped the floor with that Busa, down to a 1000 which many say could kill the Busa and the 14 up until it's top end of 170ish at which point those other two bikes wil leave it for dead.
I have very good self control. Have I pushed the bikes? Yes, but only on dead late night highways where there isn't a chance someone is going to come out of nowhere and kill me. As for handling the Busa and the ZX14 are hyper bikes which technically are tourers, so they are tanks, have more forgiving suspensions and don't like corners as much as the smaller bikes.
Now when comparing 600's to 1000's, you also need to take into consideration the years differences. Like I stated before the 05 600RR weighs just about the same as my 08 1000RR and the geometry on my bike is actually better, so you get the same weight, better geometry and more power....gonna be a much quicker bike overall. Now if you compar my bike to the 08 ZX6 and the 600RR you are going to have a better handling bike in the smaller package since those bikes were also redesigned through the years.
As for the 750, I wouldn't bother man, yes it is a bit better of a performer than the 600 but I don't believe it's worth the coin to buy into one or to switch yours up unless you get a killer deal on a motor swap.