I firmly believe that under perfect conditions (height of bounce, preparation, technique, etc...) the one hander is better. Sadly, your opponent is trying to make your life difficult, and therefore that never happens. Since this thread is hypothetical, and we are talking of potential and not real world application in realistc settings, the one hander will win. In all practical applications, the 2hbh will be better if the player has a one handed slice.
winter makes it hard to practice serving. off again on again til spring....sigh