Another option that hasn't really been discussed is... who is your target market? Are you targeting new smokers who don't know their ear from a hole in the ground? Or, are you targeting experienced smokers who have opinions?
New pipe smokers are faced with some many decessions when they decide to pick up the pipe for the first time, having to choose if they want a coating or not is just one more blind decession. Experienced smokers, on the other hand, obviously have strong feelings on the matter.
If you are targeting experienced smokers, I think offering an option is you best bet. If you are looking into mass production and lower costs, you might be better off making a decesion and sticking to it.