Both are really fun, but i like COD better from a realism stand point. Basically i get to use weapons that are historically correct or are based on real-life weapons
First of all its hard to compare a sci-fi game to a modren shooter I would have to say halo veichles mutiple enemy types forge theater and many more not to mention a story line through the entire series
halos repetetive, and to top t off they baisicly went down on call of duty. reach is a complete copy off of the cod4-mw2 game type(multiplayer). sprint, perk like customability, iron sights, classes, dam why not call it call of duty future warfare
you'll notice how most of the COD votes are 1-2 words, none of the Halo ones are like that. That says something about the general intelligence level of the CoD community in comparison to the Halo community
i perfer COD just because they both have ok costomisation, but when you look at black ops it has a lot more then the halo games. that's the only reason i perfer COD better then halo.
and for your information i have both an xbox and a PS3, lol so =P