i'd stick w/ 2" x.120 wall on an exo. part of the point of an exo is to save the body, so if the cage crushes into the cab, have fun fixing both the cage and the cab.
1.5" will crush in a good hard multi roll pretty easily, but will hold up fine in a minor roll.
chromo is a bit overkill for low speed rock crawling rolls and is left for the race cars and baja guys. if you know how to work w/ it, it does earn extra bling points.
of course the most important is the design, mounting, etc.... doesnt help if your seats rip out and you get ejected thru your cage.
i have been upside down a few times, so stonger is better... you definetly think about it when your about to go over, and then as you sit there dangeling from your seat belt afterwards.