Well, i havnt played 3on3 yet so i cant help you there but march of the minis has kept me busy since i got it not for the shipped game but for the level making feature. i love creating levels.
it comes with this level editor and you can drop spikes and pipes anywhere you want in a grid. when you are done, you have to win your level without loosing any of your characters. once you do that, it is UPLOADABLE. and others can download your level to their DS to play it.
I recommend it if you like creating stuff.
I wouldnt recommend it for the game itself though. its pretty short and easy... Although I didnt really win it on the difficult level yet.