We were in Orlando 8/29-9/5, mostly at Universal but we did spend 12 hours in MK on the 4th. Both Universal parks were DEAD all 3 days we were there and everything was a walk on. MK on the 4th was awesome, we walked on everything all day except 7DMT. It never got higher than 50 minutes and often was at 40-45. BTMRR and Splash both never got higher than 25. PP got up to 60 but we'd done it earlier with no wait and a 10 minute wait.
We were in WDW for a week last year late Aug/early Sept. including Labor Day and found crowds low, but since we only did the one day in Disney this year I won't compare except to say again that our day in MK was great!