As somebody who doesn't usually have more than one "shooting" engament between trips to station (ie. a pirate) I may give rails a go. Thus far I've been using lasters/gimballed M-cannons.
My advice on the railgun:
The most important aspect is the hardpoint placement, the class of the rail is secondary.
A C2 will inflict more damage per hit, than a c1, but a c1 allready has enough power to obliterate most subsystems with 1-2 shots.