The reason given was that the JAR-FCL requires more in terms of skills learnt and quality of how well you know said skills.
HA ha ha ha haaaa... errr, no.
The skill sets may be slightly different, but the level of skill for both FAA and JAA are high. FAA for instance includes night flying, figure 8, and flight around a spot which JAR doesn't. JAR (I've been told) places more emphasis on PFLs.
But both require you to demonstrate those skills to a high standard (at least to prove to the examiner you're not about to kill either yourself or anyone else).
Check LASORS for the skills and exam requirements. Lasors 2007 gives 3 scenarios:
- current issued ICAO licence with more than 100 hours (Air Law and Human Performance and limitations theory exans and flight test only needed. If you want the FRTOL aswell then also need the communications theory and practical)
- current issued ICAO licence less than 100 hours (full credit given as long as JAR-FCL flying experience criteria have been met, otherwise training as necessary. All theory exams and Flight test needed)
- lapsed issued ICAO licence (training as necessary, skills test and all theory exams)
The question is, why do you need to convert to JAR-FCL? You can fly G reg VFR in the UK on any ICAO licence. If you do want to convert, wait until you have over 100 hours to do it.