do believe the FAA one is more thorough, but this is just my personal opinion.
That's the most comical quote I've ever heard with regard to Instrument ratings!
The FAA > JAA route is in 80% of situations NOT cheaper.
Having instructed in the US as a JAA instructor recently I am firmly under the impression JAA
initial Instrument ratings can not be done outside JAA airspace. However, under special circumstances sometimes the IAA has tested initial IRs in the US. Any rating issued under this arrangement is a national dispensation and NOT a JAA one, and therefore does not have to be recognised by another JAA state. So you would be ill advised to take this method.
You can train for them in the US. I know one school which gives 25 hours single then 5 multi, before returning to the UK for the rest of the training. A lot more aircraft time than a course in the UK.