Depends on the situation and the game mode. Even crucible events call for different things AND, something people don't mention a lot, it's nice to have the option to change your perks up once in a while. Double jump/blink, invisibility/weapons, golden gun and throwing knives/arc grenades and sprint speed/slide. All kinds of options and you just add to it with exotics. Now that I finally got P&T, good luck even seeing me on Skyshock.