this is a tough one! it reeeeallly depends what you’re looking for, who you’re traveling with, etc. we’ve stayed at: AKL, CR, BC, GF, and we’re staying at Poly next month. i love them all, and would stay at any again, in the right circumstances (for example: i don’t think i would stay at AKL for a short, park-heavy trip)
as for split stays, the same applies. we’ve done them often and really enjoy them, but we visit for longer stretches and only with each other/other adults (until now). our next trip, we’re staying put at the Poly. we’re traveling as a family of 3 for the first time, and that feels like enough of a learning curve. i think it’ll be better to plant and stay put with a little one in tow.
edited to say i voted for AKL and BC because both have fun theming and experiences unique to the resorts, from watching animals to floating around SAB.