Honestly, it depends on what you hope to accomplish and your priorities. I have had 6 full days like you and did everything including Universal. If you want to have more lounging time and be able to repeat things then I suggest cutting out Universal for the extra park day at Disney. If you don't mind being rushed then do it all. In the 6 days I was there we did 1 day Universal, all four parks (Magic Kingdom was the only repeated one), Cirque, Both Water Parks, Mini Golf, and Dinner at ESPN for Thursday night football. We did almost every single ride, some twice, but it meant very little rest time for us. We were definitely exhausted by the end of the trip. However, we didn't know when we would be back and we wanted to accomplish everything. We made it work and sometimes we would cut out a ride or show that wasn't as high of a priority to have a little more down time in the hotel, however we would get lucky. We never closed any of the parks though which helped, but we were there at rope drop. We saw all of the nighttime entertainment.
So if you know what is a priority and if you want to be go go go or not then that would change the whole trip planning.