
I generally prefer the Heavy Cannon line for it's extreme range. About the only time I'll prefer beams is when I'm fighting Liir - they can often dodge cannon shots. For straight DPS, HFC gets 93 dps at optimal range, which is a distant 1100, and 45 dps at extreme range, which is an impressive 1600. Heavy plasma is a bit less impressive at 56 and 28 dps in the respective ranges, which are slightly less. All cannons get very slightly less dps at short range than at extreme, but it's not a large difference.
Neutron cannons are 50 dps up to 700 range, and positrons are 70 dps up to 800 range. So both are better than the respective cannons at short range, but their maximums are quite short - less than heavy cannon optimal!
- nickersonm