Hi Brunette! I have stayed at everything between 3 and 5* resorts. I think the main difference is the level of luxury provided. The quality and level of upkeep of the architecture and furnishings is a difference. (For example, in the lobby and your room, some places will have marble, fancier furniture, art, lighting etc and some will be more basic.) The number and of onsite bars and restaurants and how well they are staffed and stocked will be another difference. There will be more entertainment and pampering options at the higher rated resorts. I haven’t found much difference in the level of cleanliness at the various places I’ve stayed. They have all been very clean, the beaches relaxing, and the tropical gardens well-manicured.
What you want is value for money, right? We usually travel with children so the places with fancy accoutrements are generally not worth it. (Those are for Mom and Dad trips only!) We recently stayed at the Gran Ventana and the food was excellent, the resort was above average in every way, and the price was decent. It is not super-luxurious but it is a very nice resort which I have no trouble recommending. I believe it is rated 4*. I guess your choice will really depend on what you’re looking for in a holiday. So just keep asking questions and have a great trip when you figure it out!