Hi! I have stayed at Couples Negril and Couples Ocho Rios and Moon Dance Cliffs. I have visited MDV but not stayed there.
Couples is a really beautiful hotel but it is totally different from MDC!
Couples hotels are massive properties in comparison to MDC. They have many restaurants, bars and lots of nice little qualities that make it a really nice hotel... For example, they have a turtle at one of their hotels, lots of grounds to roam around, tennis courts etc. etc. Most of the rooms are really nice, depending on if you stay in the refurbished part or not, but then that depends on whether you like your rooms modern with tvs etc or you prefer to totally get away.
MDV is a different setting. The hotel is much smaller in size, there are not loads of bars and restaurants no grand lobby. But I would imagine that because of the size you get a much personal service and you get to spend more time with your guests. I was told I would get a private butler, chef and house maid with the villas. The rooms are big and spacious, although a little dated TBH. MDV is more of a home away from home. I prefer MDC because of the open layout.
Also Couples is only couples only, whereas at Moon Dance you are allowed children... so it depends on what you are looking for.
Hope this helps.