If you just look at damage dealt over a certain length of time, yes.
There's some nuances to consider, though. Multiple weaker shots are tougher for fighters to fend off than a single, more powerful shot. (Not an issue, with Terran Huge Turrets, since their regular rate of fire is so slow, with travel speeds to match.) Five triple turrets also don't provide coverage as thorough as fifteen regular turrets would. Given all of the blindspots in the Orion's defense, that's a pretty important consideration.
TrashMan, I think that the issue of the Faustus' multi-turret firing different weapon types derrives from the fact that one of those weapons is a primary weapon, and the other is a secondary weapon. You'll also note that the Akheton turret has a second primary slot that has a weak yellow blob laser assigned by default. Ever see a blob fired from the multi-turret? Probably not, unless the mission/table modified the turret's loadout.