PCP or CO2 is definately less fatiguing than muscle powered designs, especially over a 60 shot match with sighters as well. Theres other advantages too for instance muscle powered designs usually disturb your grip between shots, not so with PCP or CO2.
Some put high regard on relaxing or re taking the grip between shots as it helps restore circulation in your arm & especially to your hand between shots. It's a long match & at any level any help you can give yourself is probably worth it, in some regards it's a little like free pistol shooting, neither ar easy, but they seem to share certain similarities in technique.