Honestly, what Bryce said. Just do the main missions they give you and reap your mission rewards back at the tower. Equip whatever has the highest number or the best effect according to your play style.
In terms of rating, 44 helmet 36 arms, 48 chest and 32 legs. The only other thing to note is the intellect, discipline and strength bonuses on the green armor. Also all but the leg armor gives a bonus so just make sure it's what benefits your specials and guns of choice. Other than that no brand really carries better ability than another. I think it was Bungie's way of encouraging player uniqueness. Probably you knew most of this and I agree probably a bit long of a reply but just figured I'd leave the answer out there. Oh and with weapons it's level 57 and 62 after upgrade.