YOUR INTEREST IN ANY PARTICULAR PARK OR RIDE WILL MATTER THE MOST.
But its more likely to "do" AK and MGM in a single day.
Find a MORNING EMH day at AK, and go EARLY
Leave by 3 or 4pm to go to MGM and stay and "ride" until time to view the LATE "Fantasmic!" (assuming there IS a late "Fantasmic!", which would be a good day to attend).
Alternate would be to pick a day that has EVENING EMH in MGM (but still start as early as possible at AK that day.)
This is really all dependent on the time of year you visit, your interest in "doing it again", and your ability to move quickly, having a PLAN, and LUCK, LUCK, LUCK.
As for me, I want to visit all parks over several days, over separate trips made several times a year.