I'd say Contemporary Resort. We loved the Bay Lake View, and then when we were around at the time of the MK fireworks going to the end of the hallway that was closest to MK and watching them from the open outside stairwells. They were less crowded than the 4th level concourse. MK view for a room would work as well, but we found the Bay Lake View so relaxing and loved watching the electric water parade from the balcony.
Wherever you chose, I'm sure you'll have a lovely birthday/anniversary celebration.