Imo, gimballed will always do more damage than fixed at close distance (<1.5-2km) irregardless of skill. This is due to the fact that it has a firing arc that is much larger than for fixed weapons, meaning that even if you are Space Robin Hood with fixed guns, the gimbals will get a lot of hits that it is simply impossible for you to get. Even when people chaff, gimbals do decent close range on the viper since the guns will run back and forth on the target (time your shooting

).
On the flip side, fixed is much better for hitting at range, with gimbals losing a lot of DPS at range due to missing more, so to each his own. Running a mix is always an option too, and can help to mitigate some of the disadvantages each offers.
Personally, I run 2 C1 Gimballed Beams on the top, and 2 C2 Gimballed Multi-Canons on the bottom. I laugh at most pilots with fixed weapons as I dance out of their arc with my gimbals keeping pressure on them.