Is there any reason to use laser weapons over plasma, or 9mm over 10mm?

Considering that you get access to both at roughly the same time...plasma is obviously superior to laser, and 10mm is clearly superior unless you have the grunt perk and use Maria.

Unfortunately by the time you get Maria, its pretty obsolete, especially if you get it at the fort.

I also never really saw much use for the service rifle...too hard to repair, doesn't do enough damage per shot or DPS.

laser is weaker compared to plasma, but... plasma fires a hella lot slower.
and about the pistols? i usually just use the 9mm because it looks cooler. imo.

Revolvers are generally better sidearms then either 9mm or 10mm guns, but as for the laser versus plasma, like everything else in this game, it depends. Plasma is more powerful, but it doesn't fire as quickly or precisely as laser.