I've stayed at both (well, Tomamu, not sure which tower tbh). The Hilton is great, unparalleled slope access and ski valet makes it simple.. late checkout is an interesting one, as generally you would be flying out and the last bus in time for a late checkout would get you to the airport too late I would have though. Bear in mind even cutting it fine you need 4 hours from departure of hotel to your flight.

ignoring snow and terrain I'd say Niseko still, but from the sounds of your previous trip I reckon you could have an absolute blast at the tomamu resort too.

hilton niseko treat you pretty well. Not amazing like it used to be but still decently.