Ok, so I have heard from someone that regardless of whether you farm Stage 10 or Stage 15 of a particular potion dungeon, the drop rates for the various potions are all the same.  So basically, you have no better of a chance getting a superior potion in Stage 15 than you do on Stage 10.  This person has been playing for quite a while now, so I assume they are correct. 

Just wanted to check though and make sure that there is no noticeable difference as far as the potion drop rates between dungeon stages 10 to 15?