I haven't invested in other systems simply because I don't really have time to play all the GC games I get. However, if I did have multiple systems, you can bet I'd be looking for the best version every time. Most ports get the shaft, and I'd rather have one done by the original team than some half-finished product that was sent to a port team to re-code.
Speaking of shafted ports, last night, one of my friends rented several copies of Wolfenstein for Xbox, since it said it supports 16 players. Well, after spending half an hour trying to set up a six player game, we went to the website and learned that there's absolutely no split-screen mode and if you want 16 players, you're going to need 16 Xboxes. Now I know this isn't something the PC version had or anything, but from a console gamer's perspective, it's absolutely ridiculous to require anyone to have access to that many machines. So anyways, we went back to eight player Mario Kart (which despite it's shoddy implementation, can at least be done with only two Cubes.)