I just bought a 2006 model.
See anti bling thread

I cant really give you any advice on the bb, and that is pretty much the only difference i believe. Well that and color

Oh , rims maybe. Isnt the 2005 MA3 and the 2006 Open Pro Sport ? Maybe they are the same rim, diff name, shrug.

Color. This is the other difference. Mines day glow orange, its freaking bright Its so ugly I love it.

Frames are same, warrenties would be same, etc.