Our primary interest in MGM is seeing the shows and meeting characters (our son's too small for the rides), so do you think there's any advantage to getting to MGM for the extra hour? Are there many characters out and about that early?
If characters are your thing, then EE(EMH) wouldn't do much for you. In that extra hour for resort guests, only select attractions are open and I doubt characters will be out. So no need to wake up the extra hour early.
If you are a morning person I'd say go for it. On one of our trips my DH took my older thrill seeking DD on all the rides during EE and I stayed with my younger DD who wanted to see characters. We found the entire Pooh gang on a street with almost no one around. Lilo & Stitch are also now at MGM although they might not be around for EE as soon as they are you'll already be there. There are almost always characters greeting guests in front of the park in the morning. You'll be able to take the time to say hello while everyone else rushes past
I'd check the list of EE attractions and if there are enough you are interested in it would be worth it just to have a lazy start to the day. If you got there an hour late the EE crowd will have finished with the big rides and have moved to the attractions you are most interested in.
If you do MGM on a non EE day there is also an advantage that the big crowds are trying to do rides first so you should be able to have a little time to yourself on those days too. I think I'd opt for this if you don't want to do EE.