Always thought railgun would be alot more powerful
Railguns are more powerful but require maintenance after only a few shots I think. I would think that the UNSC would want their MACs firing as frequently as possible, using as little materials as possible.
Did a quick google search and found the following quote:
> A coilgun on the otherhand is the best option because it can be soaked in polymer and fired underwater whereas a railgun can’t cause it needs direct current going through the rails, it has less recoil, lower rate of fire, higher efficiency, but lower velocity
The forum discussing the difference between the two was discussing hand-held options, but the principle still applies to larger ship-mounted guns.
Coilguns might be a bit weaker in terms of impact but overall effectiveness is better for the coilguns.