I recently bought a '12 Silverwing, having just unloaded my '09 TMAX and '09 MP3 400. My purchase decision was heavily based on availability of ABS, which is unavailable on either unit (in the US - Europeans have had ABS TMAXs available for several years, the MP3s don't offer it). I won't ride paved roads without an ABS bike/scooter, just my preference.
TMAX vs Silverwing - for general riding (not hotdogging) either one is an excellent choice (ignoring the ABS issue). The TMAX is roughly 60lbs. lighter and a bit easier to handle around the garage and get on the center stand. The SW is a bit more of a chore to handle, particularly re: the center stand function.
On the road, the TMAX is a tad bit more flickable but you really have to be pushing it to exceed the Silverwings capabilities. The MAX is fast and its hard not to find yourself riding a bit faster than intended. The SW has a more sedate feel but more than than adequate power and is very capable in the twisties for most applications.
The SW is a very fine ride in just about any situation and is a very stable. I'd basically say that the differences are moot unless you're into really pushing the envelope at high speed. For generally riding, whether around town, twisties or slab, both of them are quite satisfying and competent rides.
If your orientation is very high end hotdogging, the TMAX is a better choice, but don't expect to leave the SW completely in the dust. Yes, you can cut the tight curves a bit faster but you'd better be a really skilled rider to do so and the SW won't be far behind you. For a long distance tourer, I'd say the SW has the nod but its not a huge difference, either one would work.
Ergonomics are a totally personal matter, but my preference is for the SW. Its lower seat height permits flatfooting for me (5' 8.5") while the TMAX was a bit taller than I preferred. Dependability on both units is excellent and dealership/service availability is probably equal.
Overall, they are both very fine rides, but without ABS - the TMAX had to go. My riding environment is deer infested backroads and ABS has saved my butt in quite more than one situation. When Yamaha USA finally clears the old, non-ABS TMAX inventory and imports the ABS TMAX, I'll be one of the first buyers. There is enough difference to make it a fine stablemate to my SW and I always have at least two rides on hand. JMO