I think it is a matter of personal preference and priorities.
If walking to the MK is important to you, then BLT. If you're a big fan of Mary Poppins, then its GFV. You know what I mean?
BLT:
Walk to the MK, great views of fire works, shares CR amenities, modern futuristic Walt, shopping and variety of dining choices, monorail resort.
GFV:
Close to Polynesian, monorail resort, nice pool, very nice dining, gorgeous resort and grounds, has an "upscale, high society, Victorian" feel to it.
You won't know for sure until you try them all! For example, my Lovely Bride used to LOVE (still does) the Polynesian and GF before she stayed at BLT. We enjoy visiting and walking around the other resorts when we visit WDW. She never cared for CR or its theme. She only agreed to purchase BLT points because I wanted them so bad. (Thanks Sweetheart!) After staying at BLT, it is her favorite place to stay! It reminds her of Walt's vision of the future. Plus, she loves the subtle art work in the rooms.
There was nothing wrong with our brief GFV stay. The grounds are beautiful! Our kids loved the pool and play area. It just came down to a matter of preference.
She always insisted that since I was able to purchase BLT, she should be able to get GFV or PVB points when they went on sale. She isn't interested at all. In fact, she says any add-on will be more BLT points!
My point is, try one this trip and the other next time.
Both are wonderful! They both are not perfect, just different.
I'm sure our preferences and priorities will change in the years to come, but that's what makes
DVC so nice.... variety!
You really can't go wrong!