3 Cannons is a bigger drain on energy, so I am not sure a 3rd is of any long term benefit really. I also cant see a value in mixing beams and cannons, so I am not sure if having 4 wep slots up front is really all that good anyway. As far as 2 cannons are concerned I was still able to shred shields they just were able to put them back but that is ok just means more damage for me.
As I said in the "raptor vs bop" thread, the tier 5 raptor has a dps edge over the tier 5 bop (due to 1 more tactical console upgrade and 1 more rear weapon slot for a turret), it's just more difficult to use due to the lower turn rate. So, if you like a challenge and want to milk out the most dps possible, the raptor is clearly superior. So there is a good reason to use the raptor over the bop outside of tier 4, although it's hands down the winner in tier 4.
Or you could jump on the bandwagon and go BoP outside of tier 4.
For Tier 4, Vor'Cha all the way. The occasional BoP to weave in and out of battle to dish out hurt goes a long way also. The Raptor doesn't have that ability to get in / out of combat as well as the BoP. So the Raptors have to stick around with the rest of us non-battle cloak KDF and get annihalated by the Feds, since they can't withstand much.
The T4 BoP may not pack the punch of the Raptor at that tier, but if you have the cushion of a bunch of Vor'Cha skippers (which there are alot of at that tier) in the fight, you should be able to easily flow in and out of the fight using speed and battlecloak, and pick the most opportune time / spot to decloak and strike, and GTFO of dodge.
I felt supremely confident as T4 KDF when we had a coherent force with lots of Vor'Chas and a small group of BoP. The battlecruisers just attract so much attention and we can take the punishment for a while. This gives the few BoP captains the freedom to work their magic.