I have a 16 month old son. Until now he has been using primarily bottles, although he can also drink out of a?

sippy cup. I have several different brands and types of sippy cups. I would like to start to exclusively give him a cup and would like to know what the difference between the soft and the hard spout sippy cups. Which ones are the best for the teeth. And which sippy cup brand and cup have you found to be the best. Thanks.