So guys this had stumble across my mind and I was wondering what do you guys think about which is better. But I will say that I have not read any of the books so I'm also hoping that you guys will help inform me better too! But imo basing on the game I think Republic Commandos are better than the ARCS. The reason why I say that is because you don't see them at all except that one time in the Clone Wars series.

Arc troopers are elite front line troopers, and commandos are black ops behind the lines. Although ARC troopers can go on stealthy missions to, their usually on the front line destroying thousands of droids. Commandos are behind the lines stealthy, assassinating high priority targets, gathering intel, and ll that type of stuff. Arc troopers are more independent while commandos operate as a team.
Commandos use prototype weaponry while ARCs don't.

I don't know who would win, but I think there almost evenly skilled and easily as cool