We usually skip the early EMH but when we do go we try to plan early fast passes to match up with the park were in. (This way we can get back to our room around lunch when it really starts to get crowded)
I’ve found EMH are good for the more thrilling rides at magic kingdom (space mountain, splash mountain, etc.) the crowds tend to flock to the kiddie rides in fantasy land (and mine train) EMH are also great for the safaris at animal kingdom, we’ve noticed animals are more active in the early morning. Not worth it for Epcot in my opinion since the world showcase isn’t included in EMH.