Regardless of length of stay and tickets, f you're staying at the Poly, I'd probably hit MK first since you will see it when you check in, I'd be disappointed if I saw it from the check in and then went somewhere else. Although... I guess if crowd calendars predicted a much higher crowd level at MK than EP for that day, I'd walk to the TTC and take the monorail to EP instead - basically take advantage of the monorail immediately to get immersed into the magic.