Pretty broad question. As mentioned by Ines, Miami Beach has many condos to choose from. Your question truly doesn't have an answer without specifics, such as... price range, looking for oceanfront/bayfront, South Beach, Mid-Beach or North Beach.
Canyon Ranch is located in North Beach, 69th and Collins. Then you have Murano at Portofino and Continuum in South Beach, along with the Setai.
How familiar are you with Miami Beach? and what area do you prefer? There is a difference between 69th and Collins and 1st Street and Collins. These are things that will help you narrow down your choices, as it will come down to a choice of lifestyle and price range. Let us know what you are thinking.
Cristina - asking which are the best condos in Miami Beach is like asking a 5 year old in a candy store what his favorite candy is. Miami Beach's architecture is so diverse and full of choices and your price range will ultimately determine where you end up buying.
I personally love the Continuum which is located at the southernmost tip of SoBe and is a full amenity building with valet, spa, restaurants, beach......and not to mention the unending breath-taking views.
But then you have a lot of popular buildings depending if you want to be on the ocean or bay .
Canyon Ranch is HOT now and the amenities are amazing.....I can sit here all day, but at least I mentioned my favorite 2.
My advice is for you to take a trip to Miami Beach and visit the buildings and see their views and what they have to offer, it will not be an easy choice.