I'm saying that a stickerless cube will let you look at the back of the puzzle without turning it, and IMO that's an advantage by definition. However, just because the advantage is there doesn't mean that everybody will automatically use it. I think that to actually get a better time using this advantage would require a significant amount of practice, and I'm not going to do it just to win an internet argument because it would be a waste of time.
Imagine if some player wanted to solve the cube in front of a mirror at competitions. This would allow him/her to see the complete back side of the cube (similar to how a stickerless cube allows you to see part of the back side), information which is not as easily available to everybody else who will have to turn their puzzle in some way. Would this not clearly be an advantage? Is it a good idea to allow mirrors even if proponents claim that they're not getting better times because of it? Is "we like freedom" really an argument for anything?