Depends what you want .
But I disagree with "Ninja650" comment , the 650 is not a super sport bike , but it sure as hell can drag knee , , has decent power and acceleration .
Now I have a list somewere on my thread but i comes down to this :
Here is a direct copy from my other post
"Ok , 2 week update for the 650 :
for anyone wanting the sport bike feel , get the FZ6R from Yamaha , it is based on a detuned R6 engine so it sounds great , and it has tons of after market parts for it .
I love my bike but two things are driving me nuts :
-lack of after market support for the 2012 model like sport bars ..they are coming for taking their sweet time .
-The sound of a v-twin which is basically your 250 but a bit louder lol.
So if I could do it over I would get a Yamaha since they are awesome looking bikes and sound great , also the after market is there if you want to make it even better , like sport bars and exhaust .
Again no regrets and still have a blast on this thing , it is just my point of view .
In my opinion:
get the Yamaha FZ6R if you want :
A SS feel without the SS price and insurance cost .
-4 cylinder sound
-a slightly faster bike
-more fun in the long run .
-Higher revs (10k Kawa vs 13k Yamaha)
A snappy power band above 10k ( like a sport bike behaves)
Get the 650r if you want :
-more torque , power at low ends with a more gradual power increase .
-Cheaper insurance
-dependability and cheaper maitenance costs.
-Better gas millage (50 vs 42 of the Yamaha)
-better ability to put your feet down since the v-twin is narrower
-twin head lights and flush front turning signals .
-adjustable windscreen
So in the end it comes down to preference of the above things , the Kawazaki is also porpused built , were the Yamaha borrows parts from other bikes to make it , the Reviews also point that the Kawazaki is better built ..
So don't buy a :
Yamaha Fz6R if :
-you are concerned about insurance and gas costs .
-are offended by the ugly swing arm .
-are scared of snappy power bands
-are a brand new rider.
Kawazaki 650r if:
-Hate the twin piston sound
-want tons of after market support (at least not yet )
-Want a sport bike feel.
well this is all , I like the my bike , but A FZ6R pulled up next to me at the light riding two up with a girl , and he had it pretty nicely built , sport bars , exhaust , HID , and when he pulled off it sounded like a SS , enough to full anyone but a sport bike enthusiast .
I have to see how the bike feels once I put the sport bars on (whenever they make ones that fit ) exhaust and fender eliminator"