I'm not sure about rate of fire, but I know for a fact that damage per second is better with the extended range cannon compared to HE.
Assuming the wiki's weapon appendix is up to date, ER and HE have the same DPS, though HE fires slower with more damage. HE does have the big splash making it effective against infantry though. Interestingly, the HE cannon shells travel faster. :confused: The comparison I was making was to railguns though, which definitely have higher DPS than ER. The ER cannon is lighter and cheaper, so I can see a use for it early to mid game, but later on there isn't much going for it compared to railguns.
