If your a practical guy, you buy bikes that save you money, and "almost" provide as much fun as other bikes. You want better gas mileage, and you are not one of those "look at me" kind of guys, then get the 650 and have no regrets.
If you are a hooligan in disguise, someone that doesn't believe in getting old, someone that isn't scared of the odd wheelie, and you enjoy being the first vehicle at the front of that merge lane despite the guy beside you thinking the same thing, and your bike can actually do it for you. You love rolling on the throttle and feeling that "wow" in your gut as you watch the cars disappear in your rear view mirror, then get the 1000.
One thing for sure, if you buy the 1000 you won't wonder if you should have bought the 650 but the reverse is not true.