Material properties vary between different brands, but generally:
-Nylon has best impact resistance, but is very hydroscopic and is prone to creep (slow but consistent deformation from small loads).
-PET is less hydroscopic than nylon and doesn't creep (much), but has less impact resistance.
-PPA is stronger than either in every way except impact resistance, where it's in the middle. Also the most expensive.
I'd recommend checking manufacturer TDS to compare different brands.
