I like to be able to fire non-stop into my enemies, destroy them, and still have a little energy left to start on the next one.
I use the 2 APBs with 2 PDC, and unless I'm fighting a missile-heavy battlegroup, I don't have many problems. I'll have to check out the tachyon cannons, though--I'd prefer the extra 20 ls range and smaller size of the APBs, but shield-skipping is sure a pain when used against me.
Torps are nice, but most enemies have PDCs at higher difficulties, and firing at extreme range is pretty much a waste due to enemy maneuvering (except when fighting starbases, when it's quite the opposite). I really only found torps useful against ships when firing at near-point-blank range from behind, when they could strip the shields fairly quickly. Thing is, the APBs are at least as good at that range.
As for the left and right arcs, I find the time used in turning to aim at my enemy is good for recharging energy; not to mention it's easier for me to track a single target at a time. I wouldn't mind a few rear-facing weapon arcs, though.
*shrug* Difference in style, I guess.