Halo 3 is a bit different. It very fast paced and you rarely have nothing to shoot at. Although the Campaign is a little short, the vehicle sections give it a nice variety. You can also play with up to 4 of your friends in the campaign. The multiplayer is even better. Theres dozens of game variants to choose from and you can even design your own. Matchmaking is lots of fun for you and your friends. Forge and theater mode are fun additions as well. But the decision is really up to you. They are similar games but are still different.