I went with the Sparky. It mounts to stock silencer. They have them to fit just about any style silencer, with significantly less cost. Mine was like $50 for my 96 250. I can remove it quickly, just 2 bolts and a little silicone and oil to clean, but I have a FMF shorty that I usually run and just use the Sparky on stock silencer to ride Public riding spots.
The only down-side that I can think of, is that it extends the silencer making a loop-out a possible catastrophy. Power loss is minimal.