Two entirely different games that only pertain to certain playstyles. If you like CoD then get CoD. If you like Battlefront then get battlefront.
[spoiler]I'm getting both because I like both. [/spoiler]
If you have money for one, get battlefront. If you have enough for both, then get both, or if you have ~$80-$90, get battlefield now ($20 at walmart) and get battlefront when it comes out