The aftermarket heads they sell, AS THEY COME FROM THE MANUFACTURERS, are the same as you can get anywhere else...
They also do port work...which may be what everyone is referring to...
As in, if you are getting work done on the heads, buy the heads from them and then have them do it??? I don't know, just guessing...maybe they offer some sort of "combo deal"?
I have no idea who is the "best" at porting heads. Personally, I would use someone local, but that is just me...