As others said, it depends on your attitude toward switching hotels. Some people find it a hassle. Families like mine find it delightful, especially if we can structure the split stay so that the nicest or most desired hotel is at the end.
Here's my "are split stays right for you?" checklist -- apologies for repeating what some others have said above, but I agree with them.
DO YOU....
...Pack light? My family travels carryon-only and everyone's things are in color-coded packing cubes or pouches that can simply be unzipped and placed in a drawer or on a shelf, so packing and unpacking take us all of 5 minutes. However, if you like to pack for every eventuality and prefer to unpack a lot of loose items and really "settle into" a room, switching hotels might be stressful rather than fun for you.
...Like to spend a full day at the parks? Disney's complimentary luggage transfer from one hotel to the other can take most of the day: our routine on switch day is to drop off our bags for transfer before we head out to rope drop a park, stay in the parks for several hours, and then head to the resort no earlier than 5pm, to be sure our room will be ready and our bags will be waiting for us at Bell Services. If you needed a midday nap or pool break every day, and don't want to be "homeless" on the afternoon of your switch day, you'd have to forego luggage transfer services and transfer your luggage yourself, which would be a pain.
...Enjoy changes of scenery/theme? My family loves trying out new places and locations and we don't visit WDW often, so doing a split stay allows us to experience multiple themes. We try to structure our touring so that we're taking advantage of each hotel's proximity to particular parks (e.g., visiting EPCOT and HS on days when we're staying at Crescent Lake area hotels, and MK/AK on days when we're staying closer to those parks). However, if your park touring order isn't going to take advantage of your hotel's location (particularly at the deluxe one, as they're all very close to at least one park), and/or access to extra evening hours (but see anecdotal note below) you'd be wasting one of the biggest perks of staying deluxe.
...Value the differences between a moderate and a deluxe, enough to justify the cost? Frankly, my family doesn't, which is why we've only ever stayed deluxe on rented DVC points, which effectively bring the cost down to what we'd pay for a moderate. The "perks" of a deluxe resort are typically a higher proportion of onsite table service and lounge options, close proximity to at least one park (e.g., Beach Club is walking distance to EPCOT/HS, and Poly/Contemporary are walking distance or a short monorail ride to MK), slightly larger rooms, slightly more elaborate feature pools (in some cases), slightly nicer in-room amenities (in some cases), grander lobbies, more upscale on-site shopping venues (again, in some cases), and access to extra evening hours (typically at MK or EPCOT, one night per week each, with slightly shorter lines for attractions -- although candidly, we found that with unbelievably high use of G+ lanes by
DAS users during those hours, waits for major attractions were shorter than at peak daytime hours, but still double their forecasted wait times -- obviously, YMMV, but for us, extended evening hours were not an impressive perk at all, and their availability wouldn't "move the needle" to a deluxe in any of our future decisions about where to stay).
