It depends on your riding preferences. I too have a GSXR-750 (an '09) with Helibars and was looking for a more relaxed riding position. I got an outrageous deal on a new 08 Superduke. I love the bike, but would rather track the 750.
Why? Wind blast above 80 mph on the SD is significant. At 100, its intrusive. I feel I'm hanging on for dear life. Invigorating, but far from comfortable. I can't imagine what the blast is like at 140-150 mph, the bike's top speed. I've seen 140 mph+ on the GSXR and, as you probably know, its not a big deal. Far less intrusive than the SD at 100 mph.
If you can deal with the blast, go for the SD. Its an awesome bike. Its fast, has great acceleration, and awesome handling. It never fails to put a smile on my face -- unless I'm droning along the freeway. I expect the SM to be similar to the SD in this regard.
If you want the protection of a fairing, then go for the Supermoto T. I haven't ridden one because I'm inseam challenged -- in on my tip toes on the SD and the SMT is about an inch taller. But, I attended a recent KTM demo day and every one who rode the SMT loved it.
I did ride an RC8 at the demo. The riding position was more aggressive than my 750 with Helibars and less comfortable. My old bones were aching after the 20 min demo.
Have you tried Helibars on your GSXR? They made a huge difference for me.
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'08 SD / '09 GSXR 750
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