There's actually another advantage to having the FAA license also. If you intend to fly in countries that require a validation of your license (SA, OZ, etc), then it's a lot quicker, easier and cheaper to validate the FAA one. This from own experience.
Good point. But this only works if your FAA PPL is valid - meaning you've done a BFR in the last two years.
To find an FAA instructor and do a BFR, only to avoid a bit of paperwork to get the UK-issued JAA PPL validated seems a bit over the top.
But yes, if you fly N-regs regularly and thus have to keep an FAA PPL valid in any case the validation procedure for FAA looks simpler than the UK JAA one. Basically because the folks in Oklahoma don't take privacy as seriously as the UK CAA so you don't have to give them permission to release your personal details to the SA or OZ CAA.