During peak periods the evening EMH can be really crowded and not worth the time and effort. In the off-season people report little or no waits on the attractions. I can tell you that last June it was like a mad house at the Studios evening EMH.
The best strategy for any time of the year is to get to any park at or before opening....EMH or not. You can get a lot done in a few hours at all the parks before the big crowds arrive later in the morning.