APX100 in 5x4 has been discontinued (I certainly cannot get it), whereas FP4 plus is easily available. It is also a great film. I find that grain can be a problem with 400 films in 5x4 if enlargements are getting large, but FP4 plus is sumptuous in Exactol lux (and therefore probably in pyrocat. You could always take FP4 plus as well as a few holders with faster film in case of wind etc, as I do. Personally I cannot stand TMAX100, but quite like Acros, which many would say are very similar. I think they are very different. However, Acros quickload could send you bankrupt....but souped in pyro, you will see no grain at 20x24 and get hair splitting sharpness (Unlike those who claim no grain from 35mm at similar sizes). It however still retains a modern look, which I like less than the good old traditional films.