I think, as somebody posted, it is a 'horses for courses' thing.
I'm learning to fly at the moment, and I've elected for the JAR course.
I only intend to be recreational, 'too far down current career' to make ATPL an economic proposal.
My reasons for JAR is that I may want to fly abroad. Would love eg, to be able to hire, say, in Mallorca, and do a return trip down the Spanish coast as far as Gibraltar (refuelling stops appreciated!).
But that's just what I feel I may one day want to do. For the people who just want to fly in UK - good luck to you. That's what you want to do - what's the problem?
I can also appreciate the medical aspect. Better to fly in the UK on the lower NPPL requirement than not fly at all.
Financially, not much difference to me. Only 5 hrs more for JAR - and that's only if you qualify in the minimum time - so, no real difference. And you get some radio-nav training (JAR-PPL) thrown in on the deal.
An RPPL, as mentioned, would probably do for Europe. But will it allow addition of IMC and night ratings? Does the NPPL?
Better for me I think to do JAR PPL, then IMC and Night, and then Europe might one day recognise the IMC/Night as being valid throughout Europe. Maybe pigs will fly, but surely the same Euro pigs will have to take off before the NPPL becomes a RPPL?
Now, Euro recognition of IMC/Night would impart REAL freedom to a JAR PPL to fly to/from/within Europe on a private licence IMHO.
Just my thoughts