I think the primary shot's ricochet is more random while his secondary is more accurate. I think of Ginebra's rare whenever it comes to the secondary fire mode just an actual laser rather just the aiming (hope that makes sense...) I think the primary is suppose to be good at close range while the secondary is suppose to be used for long range and getting enemies behind cover...however, I find the secondary fire mode WAY better so much so that I don't see the use of using the primary fire mode.
Oh and the secondary fire mode eats through more ammo...but as Konstantin you probably wont have that issue as much