i think that when you win, you can get credits, say, up to 500 creds. nothing for losing, but the better you do, the more creds you get. firefight should have its own SEPERATE ranking system because part of the reason i stopped playing reach was because you saw nobles who were noobs and only used firefight to boost there rank. but in halo 3, you saw a 5-star general, you better have him on your team.