Question is invalid.
Different roles being arbitrarily compared to see which is better.
Its like saying which is better, a hammer or a saw.
They are both important tools.
I believe Arc Troopers are shock-troops / heavies, while commandos are more multi-purpose. Again, that is a generalization. As different troopers had a variety of experiences. Refer to Karen Travis Clone Commando books (which are canon, despite what any Disney Representative F&$k says otherwise).
Damn political correctness. It used to be at worst James Cameron with very strong themes of his beliefs. Now, they beat you over the head with it.