I was just wondering, some companions, Kira and Aric Jorgan come to mind, can use different types of weapons, in these cases single/double sabers and blaster rifles/assault cannons.

 

Is there any reason not to use single sabers on Kira or Rifles on Aric? its mostly an aesthetic thing for me but i dont want to reduce my companions DPS too much

it's purely a dmg reduction.

Blaster Rifles and Lightsabers have 20% lower damage than Assault Cannons and Double Bladed Lightsabers respectively

Blaster Rifles and Lightsabers have 20% lower damage than Assault Cannons and Double Bladed Lightsabers respectively

 

It's actually that superior weapons (Sniper Rifles, Assasult Cannons, DBLS, Electrostaves) have 20% higher base weapon damage (which translates to ~5-10% higher damage for weapon based attacks). Standard weapons (Blaster Rifles, Pistols, Lightsabers, Vibroblades, Techblades) have ~17% lower damage (1.0/1.2) thanks to how comparative determination of percentages operates (X is % lower than Y should be explained with Y as the baseline, not X as the baseline since you're comparing X to Y, not the other way around).