I haven't tried out Gears of War yet so I can't really make a comparison as of now. From what I saw though, these games look quite different from one another. In Halo, you can run and gun and still come out victorious (depending on your skill level), while in GoW it's all about the cover mechanic that the developers implemented. I guess it just depends on how you like to play the games. Plus I don't know if it's fare comparing a next-gen game like Gears with Halo.