Hi
I am in a similar position as you. A pilot friend who has been flying about 3 years definately believes that JAA is better than FAA. he said for him to convert to a FAA licence was no trouble at all, but the other way round would have been really tough. Have you thought about going for HAI, they do a FAA/JAA CPL combined course, it costs about $50,000 and takes about 14 months I think, but the waiting list is long. I was going to go there in January 2005 course but they messed me around on the start dates and now they can't fit me in until autumn of next year. As a result i am going to do my JAA in this country.
As for CFI job opportunities, I got the impression that USA offered more than UK, but that might be just bul**** I've been fed by HAI.
also does anyone have any comments on whether a FAA or a JAA IR is more usefull?
Hope this helps