Snaps. Hands down. I have been cloth diapering for almost 5 years and I will not ever buy velcro again. The diapers/covers I have (ranging from 2-4 years old) are in great shape but can't be used very well because the velcro is not working anymore. Even when I clean it up, it tends to slide across itself and pop off. Oh, and it comes apart from the fabric, so they are kind of hanging on by threads.