Yes, the 18Fs save context in an ASM int, but of course PBP is another matter. Sooner or later you will find that writing an ASM ISR is just too complicated, or else the PBP routine is already done for you. Then, figuring out what to save / restore gets to be a bit of a problem (unless you brute-force it and always save everything). The beauty of DT-INTs is that you can have one structure for both ASM and PBP interrupts, and it decodes the INT source for you if you have 5 or 6 of them like I often do.
Because more registers are saved, PBP ints take about twice as long to get into/out of than ASM ints, but if you most always run at 40MHz +, like I usually do, it seldom matters.