Hello Darryl,
Firstly the answer to your question lies with what country you'd like to live and work in. Only you know that. A JAA licence will in theory mean that you can fly for any of the JAA member states in Europe. I say "in theory" as some JAA countries are having trouble accepting this.
As for "worth" then I would have to say that the JAA CPL/IR with frozen ATPL will be harder to achieve as a result of the sillybus being changed from just CAA lines. Anyone on an ATPL groundschool will know what I mean when I say it is confusing at times to say the least. But as a result of this the sense of achievement when you pass will be greater than the FAA licence largely thanks to the question bank not being released over here, FAA questions are. At the end of the day a JAA licence is harder.
Flying for the majors in America will mean you'll have to have a degree as this is one the US airlines requirements and they usually require substantial hours before taking you on too whereas in the UK you can sneak in with as little as 200 hours if you're lucky.
Hope this helps and if someone posts on this thread called Gorky (Ronchonner) then take his post with a pinch of salt. He is here to show that there is a shallow end to the gene pool that's all.
BM.