Toppik rubs off too easy! Dermatch it isI have to agree with CB here. Get both. You can actually use both together anyway: Dermatch as the base layer and then Toppik to bulk out the hair some more.
Oh and whoever told you that Toppik/fibres can be made waterproof - that's just not right. They might just about be rain proof in a light shower, but certainly not in heavy rain or in a swimming pool etc.