Many threads on here on that topic.
IMHO, the main plus for an FAA PPL is that one can go and do the FAA IR. Which in turn requires access to an N-reg plane to get the full IR privileges.
To just do an FAA PPL, would be because it's cheaper than the UK one. But America has seen big fuel cost rises and an FAA PPL is not as much cheaper as it used to be. Perhaps 1/2 the cost of a UK one, but very much depends on what sort of a dump you live in while out there, the value of taking time off, etc.