H belt but make sure to choose your buckle wisely as the hardware without texture can get pretty scratched up. I am very careful with all of my things and there are still a few scratches which are to be expected. I have seen some very scratched though.
I vote for wallet simply because I can use my Chanel wallet everyday but can't use the same belt all the time. Happier if I can choose both of course...
Although H offers many belts... I don't like the way most of them look on me. I wear a belt several times a year - at most- whereas I use my Chanel credit card case every day. (I think LV wallets are beautiful too.)