if "best" means many years of faithful service, i would advise to look away from those with carbon fiber skin. metal skinned mufflers will last "forever". i put forever in quotes as there are always qualifications... like a traditional perf-core straight through muffler will eventually need repacking.
the staintune brand is a sealed stainless muffler with internal baffles (no repacking) as well as a removable external restrictor tip. but they sound different... more like a V8 with glass packs.
During the 12 months I had my old m900 I tried the carbon round Termi's it came with (loud & harsh) ART alloy oval, plus the standard Ducati cans. The ART cans played the nicest tune, louder on the overrun than from a steady throttle: rrrummmmBAAAAAHHH.
There is no "best" silencer.This is a strictly personal preference.Although most ducatisti prefer termignoni exhaust systems for their bikes.My personal opinion is that Akrapovic make the best sound.On the performance issue all brands are mostly the same.The same thing happens with titanium - carbon silencers,they don't have any difference on performance.
i have to agree here, best is in the eye (or ear) of the beholder.
I bought Sils (see my other rants.. erm threads) and feel that the shorter can looks killer on high mounts. Frankly I much prefer the look of high mounts on the monster but thats me.
If I had to rank Sils on fit/finish, overall quality and installation I say they are among the worse.
Sound wise they sound great, at least the 105db models. A tad loud so I wouldnt want to go on a cross country trip but around town they are fun. I think almost any brand will improve the sound over stock pipes though.
Performance? Hard to tell, the pipes are lighter than stock so ANY weight saved improves performance that just wont show up on a dyno run. Midrange feels smoother but I think almost any less restrictive exhaust pipe would do this. Looking at dyno charts from other brands it appears to be the case.
If I had to do it over I might have gotten Termi's but for the same price Leo Vinci's look the best and sound great. Keep in mind performance wise they are all going to be somewhat the same to price is a important consideration but also look at fit/finish. You want a high quality product thats going to last. Finally find a retailer that is responsive and has a liberal return policy if there is a problem.