Early Game:
PPB: It skips their sheilds (since phased sheilds are mid/late game) does reasonable damage and reasonable range
Fighters: Powerfull but defeated by PD, use it while you still can
Mid Game:
PPB: It still is pretty good but some ppl may have phased by this point
RipperBeam: It's allways fun to have
SheildDisrupter: Expensive in the research, but devastating to sheilders in close combat
Late Game:
RipperBeam: It never stops killin!
SheildDisrupter: A must have against the late game heavy sheilders
Whatever I feel like at the moment: Why not?