I have read from testimony of a high end drag racer (who would of course want only the best of the best), that the more expensive plugs made zero difference, and that he only used cheapies. Probably with a nice ignition set up and also whilst running insane compression. This was on the internet though so take it with a grain of salt.
I don't see the value in plugs, most of it is just marketing. Spend your money on synthetic oil or something instead.
as sss kiwi said though, if you are spending big dollars on an engine, might not hurt to have them in.