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.