From what I've read and heard:
1) the PC is a popular mid-top end pipe with good quality control and customer satisfaction.
2) FMF has a huge following in the KDX world, they offer two distinctly different pipes depending on the area of power you want to target, and they have mediocre quality control and customer satisfaction.
3) Dynaport offers two different pipes that are described as FMF-like pipes only harder hitting in all areas, they are starting to catch on more with riders fed up with FMF and those willing to branch out, and their quality control, attention to detail and customer satisfaction is second to none.