I am trying to zero in on my January plans with our then 6 and 12.5 year old nieces. These resorts are priced about the same (without knowing what the discounts are going to be) so which one would you pick and why
Awesome trip for your nieces!
I have stayed in each of the rooms you mentioned and I would go with the Polynesian or the AKL Club Level.
Although we swam once at AKL in January a few years ago, odds are the pool is not going to be a big draw IMO. Yes, they are heated but if it's in the 60s outside or colder
Staying club level would be exciting for the children, they can pick out snacks in the lounge and watch the old-fashioned cartoons with the other kids... Then, of course, there are the animals! Zebras, giraffes, ankole cattle, Greater Kudu, gazelles - not something you see everyday

The resort is gorgeous! I highly recommend it. There is an indoor and outdoor firepit and wonderful smoky smells from the restaurants... might be cozy in January. Also - if you do choose to get in the pool, you can really warm up in AKL's 2 hot tubs. They are HOT!
As a previous poster mentioned, the Poly is just very "Disney" so it is a wonderful choice

You can see Cinderella's Castle, Space Mountain, the monoral line, the Contemporary Resort, the Grand Floridian and all the boats on the Seven Seas Lagoon from all around the Poly grounds. It is a wonderful place to stay
Good luck with your decision. You certainly cannot go wrong.