I have stayed at both, depending on the reason for the trip. If you are going to spend a lot of time at Epcot, BW is a great location. But if your time is going to be pretty much evenly split, taking the savings at POR is a good choice.
The main question I would ask though is how much did you plan on using the kitchenette in the studio? That microwave in the room is sooooo convenient. Usually if I've booked a DVC villa, I'm planning on utilizing the kitchenette pretty heavily during the trip (for example, staying in one during hurricane season, or for a marathon weekend).
Another consideration - how many people in your traveling party? A studio has one queen bed and a sofa bed, where a POR room would have two queen beds. If you have more than two people in your party, having two actual beds makes for a much more restful sleep.
There isn't a lot of difference really in the bathroom facilities in either resort, considering they both have a toilet/tub room and a sink separate. I do like the privacy curtain at the moderates as opposed to the open vanity of the studio.
Only you can decide if the savings is worth it to you, but having stayed at both for trips of similar length, you can have a great vacation at either one.