Hi,
I've used both.
Mustela smells very GOOD! But fo nappy rash, not effective cos won't heal the rashes.
Desitin Creamy blue one is better, but best is desitin original purple, but the smell is medicinal and very sticky and tough to wash off, which means that baby's pee and poo can never touch the skin if apply enough cream!
My gynae recommend desitin original when nappy rash.