The viper is meant to be low profile, like mounted on a milled pistol slide to keep it similar to the location of the sights.
Depending on how you mount it on you PCC it may end up too low. Either of them will work great, but you need to factor in the height of the optic and size of the window.
I have a Venom and a Razor. They are in the Vortex/ADM mounts and are at a perfect height for my GMR-13.