Congrats on the ownership, or soon to be ownership!! Hope it was a smooth and fun-filled process. My daughters are 2 and 7 months old, so naps and lunches back at the room will most likely be figured into the trip.
If you are sure you are going with a 1BR, I would hands down choose BLT. This is after having had a nice big Contemporary hotel room (bigger than a studio) with a 2yo who still napped, as well as a GF hotel room (large!) and a BLT 2BR and BWV 1BR - while it is possible and pretty easy to do naps in the hotel room while 1 parent hangs out (my DH and I traded off, he just worked on his laptop in the dark room), it is REALLY nice to have another room to hang out while the kids nap. And with the BLT location, it would be easy to switch off and go to MK/Main Street for a while. I actually liked just browsing the stores and taking a leisurely walk NOT pushing a stroller or wearing a baby, and going AT MY OWN PACE.
Also, I can't emphasize enough how easy it is to get to/from MK while walking. We actually would take the kids and give them (well, the older one, last trips) breakfast or snacks on the go while heading out, and start lunch/snacks while walking back. Invariably we'd push the return time to the hotel and forget how long it takes to walk from the Carrousel out to the park entrance, and that was when meltdowns could sometimes happen. No one enjoys a melting down toddler on a bus (strollers have to be folded) or on the monorail. And the feeling to push a stroller up the ramp to the monorail only to see it pull away... !! Walking is SO much easier.
That said, Poly is on the bucket list for someday (though their lack of 1_br is a bummer) and we love GF so much that we are going back this summer (it's our 5yo's favorite resort, and probably mine too, overall). But it is also a LOT more expensive, both per point and also for total points.
If you decide that you're not going with a 1-br but instead will be staying in a studio, then I would so go for GF or Poly! Maybe Poly because of the ease of monorail access to 2 resorts. But GF has lots of princess stuff (1900 Park Fare and also a princess parade where you can meet Cinderella and Prince Charming), if that's something your older daughter likes. You really can't go wrong.