it's really, really, REALLY a sidearm
the pistol is versatile as all hell but is out-and-out overcome by any primary weapon
so it's best used for picking off enemies you've already damaged (or can't damage in the first place) with your primary
the magnum is very similar in versatility but it sacrifices just a little for sheer viscerality and awesomeness factors
(also, it 2-hit kills on headshots.)