I am running a Neu 1515/1.5y on 6s and it is very great. Awesome power, and stays very cool. It really depends on how you use it. You can't go wrong with the 1515/3d, 1515/1.5y, or the 1515/2.5d. They are all very good 6s motors.
If that's the one I sold you a few month back I glad to hear it's working good for you!..