Railguns have good dps at close range, as said - and a even 12 or 15 cm rails can be quite servicable as PD. You get less barrels total, reducing the PD capability, but gain some range. As long as your reload speed is still below the time you expect successive missile volleys to land in, there's no issue with that.
Or go with turreted lasers, 10 and 12 cm ones get 5s reloads at cap recharge 3 and 4 respectively. They're not quite as good PD as rails, but have a bit of range and punch. Good against beam fighters and FAC, too, and the option I went with to arm my carriers.
The problem if you're slower than the enemy is that you need a range advantage. If your fighters aren't home/out of ammo and somebody with reasonably large guns (= range) comes along, you have a problem. Consider a single spinal laser for being able to punch out at range to prevent any small ship faster than you from kiting you. Or carry a small set of beam fighters!