Like was mentioned, SVSF has narrower lower clipons. I almost got one as well, and rode around on an older used half-faired S for comparison (same thing though).
The Wee will give you awesome fuel economy (dunno if its those dual-sparkplugs heads or what), very comfortable ergonomics, and big compliant suspension that doesn't care how well the roads are maintained (or light-medium offroad for that matter), a 300 mile cruising range, amazing headlights if you ride at night, good aftermarket, and it takes really well to "get'n'r dun" and doesn't look goofy with a top case hanging way off the back of the bike 2-miles in the air. With a bash plate and crashbars it just looks really rugged too.
It won't be as flickable though, feels top-heavy at low speed, its a little heavier, and you'll get a lot more dive from that soft front suspension.
BTW, I was considering not only the Wee vs the SV, but also Kawasakis offerings... the Versys vs the Ninja.
The Versys is even TALLER than the Wee (at least it felt so to me), but its a overall direct competitor. Reviewers say it doesn't do as well in offroad, but its the slightly quicker bike on the street. It has a 17" wheel up front w/ means more aggressive on-road only tire options. Headlights aren't as good, looks kinda goofy w/ a rack and has a rather slender tail though, and only comes in red so far. The Ninja 650R compares the opposite way to the SV. It again is a direct competitor to the SV650, and actually is slightly more fuel economic, much much more upright, with a softer suspension.
Both worth a look at though, if nothing more than just feeling that much more confident in your decision when you do get a Wee. Everyone has different needs though, and there are lots of awesome bikes out there.
They are both great bikes, i have both, but from a commuting standpoint, the Wee is the way to go, better mileage, more comfort and less wind
With a madstad or aftermarket shield less wind... otherwise you get blown all over the place in the turbulence! Stock is kinda sucky IMO.
BShelton, have you considered a sport-tourer as something to look at as well? If you're 100% onroad and you have a healthy budget to work with, for two up touring where you can still take the bags off and have some fun I'd look at the new Concours 14 from Kawasaki.
Don't worry, you can replace that horrific looking bazooka exhaust with a lightweight aftermarket slipon:
A 2002+ used VFR Interceptor would work as well. I wouldn't get a new one though, as depreciation would be big since I believe next year they are totally revamping it.