If cost is your biggest factor in the decision, than its hard to argue the studio at VGF. Im not sure what the difference is on a per night, cash-basis, but it appears to be a 50-60% difference in terms of DVC Points. I would have to imagine a similar correlation on a cash reservation.
If money were no object, its no question that a 1BR at BLT would make for a more comfortable stay. As others have mentioned, having a separate, private bedroom, full kitchen and second bathroom are huge perks over the studio at VGF. But if youre anything like me, I view my rooms at WDW as a place to lay my head at night. I use the rooms for sleeping, showering and a place to store my luggage only. I didnt buy into DVC for the opulence of the rooms.
If I were in your shoes, and you feel that you can handle a week together in a studio with no privacy, then my vote is for VGF. Id love to stay here while it is brand-spanking new, and youd be saving money over the BLT 1BR. But having stayed in a 1BR @ BLT, I can tell you that the room really is incredible, and being able to walk to MK is a nice perk. You really cant go wrong with whatever option you choose.