I don't know if this is on point or not, but I'm thinking that the renders are different because the render settings or the scenes aren't the same. A while back, I made a small scene to look at some new purchases. For grins, I made the scene in P5, saved as a pz3, then loaded it into P6 and rendered with the saved settings. There was absolutely NO difference, not even a pixel (that I could find). I timed each render, and even that was the same. FWIW