Oh, also.. I don't want a can I have to re-pack every 5000 miles...
if you can still get one, go for the buell rce muffler or drummer.
the buell race muffler has the best low-end output.
drummer has a lower thumping sound, more harley like. (100-105db)How loud is the Jardine vs the Drummer?...thing is, I want more "get out of my way" volume, but, not so much that I get an annoying drowning on the highway.
jardine has it's own low sound with some (i think) cool backfire blows when releasing the throttle. it is also louder (110-120db)
difference in traffic, with the jardine people will make room for you.
when in a traffic-jam, bike's (even ducati) let me pass so they can ride behind me because people hear me coming and make room.
performance wise, drummer is the better choice.
please note that what thundersteve copied, that muffler's which use the same model for both the 9 & 12 can have totally different results on each model.
logically, a specific model manufactured muffler should perform better but will be more expensive
as lucas already mentioned, here is a shootout with the most common exhausts.
both on the 9 & 12, with soundfiles (live sound is still different) and dyno-charts
download <<here>>