This is often the thing I most doubt about. It depends, if a CPO is shot (which they always are), than of course restore it. Is there NOS ? Great buy it and use it. No NOS ? Are there good repro's ? Then go that way. Of course the best of the best is when things happen like Rich from ThisOldGame is now working on (SW cockpit full artwork set from the original Atari films. When that is released I will definitely get it and install it. Even though most people will probably rate the current side-art as "good", I see loads of damages, scratches, wipes etc etc etc.
But for the Galaxian f.i. I chose not to do it. The available repro's are not on vinyl that looks anyway near the original. Yes there are a good number of scratches around, but for a 1980 cab, it looks pretty good really.
So it's a bit of a balance between how bad you rate the damage/current state against what is available in new artwork.
Where will you get the WOW artwork from ? Here:
http://www.phoenixarcade.com/art.htm#WIZARD_OF_WOR ?