They feel very similar power wise, but power delivery is totally different. My impression of the SV is that it's pretty weak under about 6000 rpms, then really opens up. The Thrux is strong everywhere, but really gets it between 3500-6000 rpms, especially if you put an open exhaust on it, and get rid of the airbox. Sounds fabulous too.
The Thrux feels torquey while the SV feels a little peakier. Also, the Thrux will feel the 100 odd pounds heavier, and a few hp short.
My 865cc T100 has predators and airbox removed, also I went down to the 17t front sprocket and I can hang with my buddy's stock '05 SV650, although he is probably a little bit faster. I'm about to change all that with a big-bore, some headwork, and aftermarket carbs though...
The Thrux/Bonnie vibrates a lot more than the SV does, which is not at all.
The SV is a better handler on serious twisties, but the Thrux is no sloutch. SV has better brakes.
Thruxton is way cooler.