Hi Intel55
Sorry for the delay in responding
Well I suppose you could say propane has a problem with low vapour pressure compared to hydrogen, giving problems with liquid propane forming in the lines and keeping consistent pressure. But these problems can be overcome by using vaporisers.
Hydrogen burns cleaner and slightly hotter, usually produces higher velocity spraying and with some coatings has the edge on coating quality.
One cylinder of hydrogen requires about 1/2 cylinder of oxygen, while one cylinder of propane requires roughly 5 cylinders of oxygen for complete combustion. Roughly you need 10X more hydrogen by volume for spraying than propane (oxygen roughly the same). Hence propane has one very big advantage - cost.
So I would conclude that hydrogen is not necessarily the better overall gas to use and would only recommend its use on some coatings where absolute high quality is demanded.
It would be interesting to hear opinions from those that regularly use both fuels.