To me, the important this is that the plate orients the camera accurately so that when the ballhead or tilthead (or whatever other head you might use) is in a 'neutral' (i.e. 0° or perfectly level) then the actual angle of the camera matches the level on your tripod and head. This is particularly important for panoramas etc.

As the guys mentioned, any plate fixed to the camera, regardless of manufacturer) is potentially going to leave some marks because you are tightening a steel object against the softer material of the camera body.

For me, I never take the plate off anyway so I'll never notice any marks. However I do understand how precious that new 5D3 would be to you, at the end of the day it'll eventually get marked from bumps/knocks anyway.