Don't forget that your trip to the US for a standalone FAA PPL will most likely require an M-1 visa and TSA approval (or at least the succesful submission of fingerprints). Going to the US to get your 61.75 "piggyback" FAA PPL plus a BFR requires neither.
Also consider the medical requirements.
AFAIK the 61.75 FAA PPL can be flown on either a JAA class 2 or an FAA class 3 medical. But for the standalone FAA PPL you'll need an FAA class 3.
It all depends on what you want to do eventually with your FAA PPL. If you're only going to have a flying holiday in the US then the 61.75 process is good enough - and actually that's what it was designed for.
If you're going to be flying (owning?) an N-reg for a longer period of time, possibly outside the US and possibly add ratings (IR?) to it, then the standalone FAA PPL makes perfect sense.