Originally Posted by Medion
Using a modern GPU, you cannot get better graphics using Glide over D3D (assuming the game isn't glide exclusive), because all the Glide wrapper does is convert Glide calls to D3D. It's a translation layer, nothing more. It should only be used for older titles that were Glide exclusive.
If a game implementation for some reason has more bells and whistles under GLIDE, it will look better. (had a vague memory Diablo 2 does, but I guess I could be wrong there)
But API wise there shouldnt be a difference, as you say, if the game is designed to run the same stuff under both APIs.