First off welcome!! It’s a tough choice but if I was forced to choose and MK was my park of choice for day #2 I think I’d go with the Polynesian. Staying at the Poly would definitely give you an advantage to MK for sure. The walk is beautiful. I made a video of the walk and I’ll enclose it at the bottom of this message. The only flaw would be the check out process but you’ll have the same scenario at either resort if MK is your day #2 park of choice. Since you won’t have a car, you’ll need to call bell services the night before and set up a time to have them come gather your bags prior to your walk over to the park. Or you’ll need to lug them down to Bell Services yourself early in the morning. Keep in mind it make take a while before you have access to the bags once at YC. Usually after 3pm so if a mid-day break was on the schedule keep that in mind. The good thing is you’ll still have access to the Poly pools/hot tub areas so if a mid-day break included some pool time, it’s an easy boat ride from MK back over to the Poly.(don’t forget to pack a bathing suit in your park bag that day) Also, there’s more food options available at Poly right now if your mid-day break calls for a meal outside the park.
As for AKL, I’m not sure how many are in your group but the 1 bedroom would be my choice. Savannah view is nice but you can see the animals from so many spots within the resort itself and a Savannah view won’t gaurantee you the best view anyway. I’ve stayed value studio, Savannah view studio, and 1 bedroom standard view in the past few months and we actually had a better view of the Savannah from our 1 bedroom standard view vs. our Savannah view studio. The extra room and the kitchen in the 1bdr is definitely worth it as well. YMMV. You’ll have the same issues with your bags in the morning getting to MK but your options for getting to the park is now limited to the bus.
Either way it’s a good dilemma to have and you can’t go wrong with either choice. They are both beautiful resorts. Enjoy the vacation and the link to that walk from Poly to MK is below.