I have been playing with both for well over a year. I honestly find no difference in looks whatsoever. Here are a few comparative videos I've shot of them:
[ame=http://www.youtube.com/watch?v=iPKuSrrnqFk]Opti Coat vs. Aquartz - YouTube[/video]
[ame=http://www.youtube.com/watch?v=UA598dGjHE4]Majestic Solutions Ultra Gloss - YouTube[/video]