The difference is far more to do with medical requirements than hours taken to get a licence of either flavour. I have both PPL(H) and PPL(A). As I only fly day VFR in the UK, an NPPL(A) would be perfectly adequate for my fixed wing requirements. However, as there is no such thing as an NPPL(H) and I am over 50, I have to go though all the cost and rigmarole of annual Class 2 medicals just for my rotary licence. Hence the existence of an NPPL(H) would be of great benefit to me and many others like me.