I have stayed at the Hyatt Grand Cypress and our family really loved it because of the incredible fantasy pool(same as the Hyatt Maui)BUT my kids are 8 & 11 and quite tall for their respective ages and we found the pool quite deep. They are excellent swimmers so it wasn't a problem however the shallow areas for little ones are very limited. Also, that huge pool was cold in early Oct, I cannot even imagine it in Dec. I am running on the assumption it is not heated but check before taking my word as law.The water slide is not a big one but it is fast and seriously fun. The lobby is impressive, the staff was courteous and professional and the grounds were gorgeous. The rooms felt like a trip to 1989 but I liked them, it was nostalgic and they were clean and upscale 1989. All in all, as I said before we loved the hotel but I don't know if we would have if my kids were younger. Can't comment on the Marriott, have not stayed there but both hotels are in pretty good locations so I don't think you could go wrong at either. Good luck...