The Omega units I've found to be best are the Viper (used in conjunction with Strykers) and the Falcon (used in conjunction with Apaches). If you don't buy the Colossus, you won't get this daily mission. You almost certainly won't be able to win a battle with the Colossus, so battles working toward this mission won't get you resources.
The 'double experience points' item helps with this, but the 'instant 500 experience points' item doesn't. Also, if you have it, occasionally you'll get a daily mission to earn 500 Colossus experience points. It's the only Omega which is defenceless against airborne units. Whatever you do, don't get the original Colossus. 2 is superior to the original - once you're able to get it, use it rather than the original. Some Omega units are available as both original and Mk.
