Without having done SA exams it's not possible to make a comparison. However comparing the US ATP theory exam (all one of it) with the UK ATPL exams (14 of 'em) then I can say from experience that the US exam is simple, quick to study for and quick to complete.
The flight test in the US, however, is more difficult than the UK one. There's an oral section before you get to the flying bit with the questions at application level of knowledge. You can be given scenarios with circumstances that require you to apply the rules and regs to the situation as if you held an ATP already. Flight tolerances are a little more difficult in some areas eg 1/4 scale deflection for the ILS, and a little bit easier for others (established - not formally defined but often taken to mean needles off the stops - instead of half scale for commencing descent)
By the way, the Australian ATPL is somewhere between the two. Theory leans more towards the UK depth (although I think a bit more practical - at least when I did them nearly 20 years ago) while the flight test is more like the USA for the ground portion, and more like the UK for the inflight bit.