A sheath urinal is designed to be worn continuously and has its place for incontinent males.  However they are uncomfortable, the tubing frequently kinks limiting drainage into the drainage bag , and they require that the male have enough length to apply it.   They have their place for incontinent males to help decrease the need for other incontinent supplies such as diapers.

A MUDS is designed to be used intermittently at each urination episode, it does not support being worn continuously and requires continence (knowing when you need to urinate) or at least the ability to be bladder trained to urinate on command to avoid accidents.