Last Sunday we went to MGM in the AM for SWW - it was PM EMH park. We had been there on both Fri and Sat for opening and until 3 PM - Sun AM was MUCH more crowded - we headed out of the park by 1PM - can't say how long the waits were as we were just there for SW stuff, but overall, the park on Sun was jammed compared to the 2 prior days - walkways were packed, extremely long lines for characters.
Had PS at CRT on Mon @ 8:10 - MK opened at 9 and was an added PM EMH day. We (mis!)figured that maybe it would make the park a little less crowded that morning as people might sleep in and come later since the park was opened until 1 AM. We were at the rope drop behind the castle at 9 AM, spent a few minutes watching Tink being awakened, picked up FP for Stitch, stopped for a quick autograph with Buzz as he walked out as we were walking to his ride - rode Buzz - headed over to Space Mt (now only 9:30) and the line was already 45 mins long !! Decided to walk over to BTMRR - 15 min wait - then Splash - 20 min wait - as we came off Splash the posted time had been moved to 45 mins at 10:15 ! As crowded as we thought the park was that morning, we could not believe the sea of people coming up main st as we were leaving at 1:00 ! My opinion is that, yes, people are choosing the PM EMH park for their entire day.