Commando: is an offensive unit that get's an additional bonus in mountains and hills. It is STEALTH and so only scout units can see it. It fights best against light armored units but is good against unarmored units too.
Mot infantry: is a very fast offensive unit that get's an additional bonus in cities and plains. They have a SCOUT ability and so they can reveal stealth units like commandos, anti tank or militia. They are best against unarmored units.
The two units are very different with a different use, different terrain bonuses. Actually Mot infantry is the perfect unit to attack commandos with when they are in cities or plains. You should never put them together in a stack.
