My husband is sort of a spa snob and he much preferred the GF. The one at the YC/BC is considered a fitness center. They didn't have the private area for the steam room, sauna and whirlpool that they do at the GF.
You can take the monorail from the MK entrance to the GF or walk just to the left of the monorail entrance and you'll see the resort boat launch for the GF and Polynesian. It's a beautiful way to see the resort and it's the first stop so it can actually be quicker than the monorail.
Tammi