Are there any bonuses when you become a pro in wii sports resort?

yes, in some sports such as sWordplay you get upgraded armor with more padding, it doesn't really do anything but it looks cool :), also when you've beaten the champion for sWordplay(duel) I'm pretty sure you get purple armor or a purple sWord, other than that I'm not sure of any other sports that gives you bonuses but becoming pro, beating a champion, or get 2000 points in a sport might give you some sort of bonus along with getting all the stamps for that sport

I've gotten all the stamps and gotten to 2500 and u get 2nd stage armor when you get to pro, samurai armor when u beat the champion, and superstar class at lvl 2000. Nothing happens if u get all the stamps. Oh and yeah, if you hold 1 at the loading screen (and you must beat the champion to get this) u get a purple sWord