That is a tough one, since I love both. Being a POR lover and having stayed there each year since 2007, I have to admit that we just stayed at the Beach Club two weeks ago and it was one of our best trips, mainly because of the resort. So much so, my next 2 trips are booked there. I thought I was going to miss POR, but that wasn't the case but I actually did miss that awesome food court. The one thing BC lacks, IMO is a really good QS. The options are just slim, but there are other places near and around the BC with other options too. Everything else about the resort, we loved. You are going in January, so I am not sure how much you'd use the pool... but that was another thing we loved. Stormalong Bay is the best pool we've ever experienced. We used it every afternoon of our trip. We really loved the rooms, and having the extra space, and mousekeeping was great. Our rooms were so close to the lobby and Marketplace (literally steps away on the ground floor), so I did not miss the long walks like we've had at POR. The transportation was far better than I've ever experienced at POR. I am so used to being packed in like sardines on the buses at POR and waiting in lines at the south depot. There was none of that this trip. We never had to stand, even with YC being picked up first. The bus stops were always empty and so were the buses. We loved walking to Epcot and the boat to DHS was really nice.
POR is great. I love the grounds, and the food court is one of the best. The royal rooms are my favorite. The boat to DS is nice and relaxing. YeeHaw Bob is a lot of fun at the River Roost Lounge. I honestly don't think you can go wrong at either resort. I just feel like BC has some more to offer. $900 is a good difference, and saving that for other things would probably be great. If I had to choose between the two, it would have to be Beach Club.