We've done a lot of split stays. Depends on what parks you'll be focusing on,
I think the best split stay for 3-4 nights would be:
BWV/BCV and a monorail resort--easy access to HS and Epcot, and then easy access to MK
I've very much enjoyed splits with AKL-either Epcot resort and AKL, or a monorail resort and AKL
that said, I think more than 3 days at AKL woud be too much, I'dl probably do a 2 to 3 at AKL and 3-5 elsewhere,
We own at BWV, and our favorite parks are HS and Epcot for festivals, and we want the option of walking to both, so we now always have BWV as part of our split
Splits are also great to just try a new resort. Like I still haven't stayed at Wilderness Lodge, but don't want to commit all my days to it. would prob do 2-3 nights there, and BWV/BCV, etc.
we always have a car, so not sure what it's like to do a split without one