We have never made it to a park at opening time, much less an hour earlier. We tend to sleep in, arrive around noon, use our FP during peak times, then stay until the park closes. We hardly ever leave before the fireworks (or whatever night show the park has). We usually try to do the 'recommended' parks, but occasionally for scheduling reasons we will be at one of the 'less' recommended parks on a day. For example, we almost always spend our first day at MK, regardless of crowd levels. We started at EPCOT once but my son kept asking when we could go to 'Disney World'

. We do notice a crowd difference, but not enough to make us leave or avoid it on future trips. That said, we also have AP or park hoppers most trips, so we often hop over to MK or DHS for late EMH and it is amazing! I can't wait to add AK to the list of parks worth hopping over to for an evening
I love the MK at midnight in the summer!! The lines are short, it is cooler, and the park is half empty. Most of the toddlers are gone or sleeping in their strollers, so my kids can walk on to Dumbo, Goofy, Little Mermaid, Speedway, and all their favorites over and over with no wait, even on peak days in July! DH and I can just relax as the atmosphere is more laid back. The last couple hours at any park are the best (especially if your family is not early risers!) and the EMH version is my favorite!
In your situation, I would probably try to go to the recommended parks, but if you find that an EMH park works better in your schedule one day, for whatever reason, then don't be afraid to try it!