RE: Bisson or Slimeline
rogcjr,
I've used both brands and either will do. Of the two I prefer the Slimline on the OS 46, but that's just because that's the one I have on mine. A more important deciding factor may be the fit of the muffler in your cowl. You can get the measurements of both mufflers off of the manufacturers websites, that way you can check and see which one fits in your cowl better.
Hope this helps
Ken