Often when a new Battlefield game or Call of Duty game is announced, fires from within both camps tend to flare up about which is better, and also why the other one sucks. This is also the case with the upcoming Battlefield 4, and Call of Duty: Ghosts. As a gamer who has played both franchises dating back from Battlefield 2 and Call of Duty 4: Modern Warfare respectively and a few beyond that, both games have much to offer for players who enjoy military shooters. For example, if you enjoy fast paced Close-Quarter Battles, the Call of Duty games might be your cup of tea, despite having some often ridiculous and crazy maneuvers that you can pull off in-game. If you're the kind of person who enjoys larger, more dynamic environments with vehicles with squadmates, then Battlefield might be the direction you want to lean into.
Despite a brief description on the type of gameplay one would expect in either franchise, this is where the flaming and trolling begins. Ironically, many opinions that are tossed out on the virtual battlefield are very opinionated and have no regards as to an openness about both the good and bad between both franchises, but rather a slew of "this game is better than that because of (insert various reasons here)". While some of those reasons have a thread of truth wrapped around them, at the end of the day, Fictional VGHS Dean Calhoun probably describes it best as its all about the game, regardless.
So really, enjoy either franchise as much as you want, because that's what really matters.