I'd say the endless replayability of Terrorist Hunts with a friend make Vegas 2 the better buy than ODST; if you're not an avid online gamer that is. Vegas has some fun online modes but Halo obviously trumps it in that field. On the other hand, I always had more fun playing Terrorist Hunts on High Density, Realistic difficulty with a friend than I ever had on any Halo offline campaign, all of which I have personally found to be run-of-the-mill.