While the actual air temperatures will likely be similar to what you experience at home, it can feel very much colder. Take warm jackets, and maybe warm hats as well. Be prepared for chilly nights.
On the other hand, it can also be downright balmy that time of year...if you are lucky. We've experienced both in mid-December. I'd take mostly cold weather clothes, but a couple outfits that would work in warm weather, as well.
As far as the best place to stay, each resort has its pros and cons. If you are looking for the best Christmas decorations for
DVC resorts, that would probably be VWL. If you are looking for larger, comfortable rooms, or two real queen beds in a studio, OKW should be your choice. If you are looking to be within walking distance of EPCOT and the Studios, then BWV or BCV would be your options. If you enjoy night life and dining, and want to be within walking distance of Downtown Disney, then SSR would be your best option, followed by OKW, which is connected to that area by boat.