I would count myself a sports fan more-so then a comic fan. Mostly because its just plain easier to keep up with...at least for me it is. 
With that out of the way, I think the only real difference I've found is that its easier to find sympathetic fans of a sport you like then sympathetic fans of a comic you like. 
Ex: at my last place of work I could go in and b***h and moan about how the Angels stumbled in the playoffs and all the baseball fans would understand to some degree; yeah there might be a few rib-kicks tossed in as well, but for the most part everyone would be on the same page and enjoying the topic.
 If I tried to bring up a certain comic series I was following, the folks who I knew that collected and kept up with comics would be MUCH harder to gell with - like I was going to have to work hard to break their clique. Whether it was me reading the 'wrong' kind of comics (Horror) or enjoying a particular creative team that they didn't it was not nearly as much fun to hang with 'em. 
Granted, this certainly doesn't apply to all cases or anything, but I have seen variations on each example time and again. It may not be much of a case, but its all I got..lol!