As far as I'm aware...
PFL Early type - standard fresnel lens as used on cars for donkeys years. 94-97. PFL
MFL Clear type / projector - the ones that basically everyone on here has uprated to - externally look identical to Xenons. MFL / 97 / R-reg onwards.
MFL Xenon - Externally identical to above clear type, but with ballast back etc. (yet to find if the actual lamp unit is the same, only the ballast back differs, but that's for another day)
All FL - small point or corner to the light unit, come in Xenon and non-Xenon. Again, look externally identical , but there's a ballast pack in there on the Xenons.
So to answer your question - no, PFL aren't the same as MFL, however there are plenty if not most, if not all the PFL owners on here which have upgraded to the MFL lamp units. And the two are of course totally interchangeable. The same? - No. Swappable? Yes.
Disclaimer: I reserve the right to completely backtrack and undo anything I have said due to technical inaccuracies, that includes marriage.