the heavy turret is of little use - if you look at the stats, it's kinda impressive, however you will not be able to fit any more then 4 for those at best. they drain your core and force you to set up another weapons group. plus, all class 5 take up precious cargo space.
the EMP however is a horse of a completely different colour! it is basically a transport flak, excellent against torps or missiles and even to take down fighter shields. it's definetly worth the cargo nerf. saved my ass quite a few times.
