Currently agreed-on weapon ranking is GAU>Minis>Laser>Rocket pod.
The GAU is the most consistent weapon the PO has in their arsenal. HV does more damage I believe.
Incend Mini rockets are a nice surprise. Normal minirockets are also great.
The Laser's unpredictable, but it deals heavy damage and is the only way to set Ravagers and possibly Queens on fire. You do, however, need to print ammo for it since it's the only weapon with no stored ammo.
Rocket Pods are a crapshoot. You're more likely to miss and waste a rocket than you are to hit anything, especially with a Keeper.