An interesting topic which has differing opinions. Since I restore games for a living, in most cases - it is a $ decision. I do get a lot of customers specifically requesting High End work to the classic Bally "Holy Grails". In some cases - money is no object, they want all components of the restoration to be as close to new as possible. These games are presented to me almost completely hammered. The Fathom I've almost done was repainted by the previous owner, and it was HORRIBLE. After many hours, it looks as good as it did when it left the factory. This is one end of the scale.
As more repro parts become available, customers can see the attractive proposition of a full restoration. It can be done - if the $ allows.
Each pinball has a story - where it came from, previous owners, non factory legs, repainted white etc etc. Some people like the charm of the nicks, scratches and scrapes. The import thing to realize is most restorations are simply a step up from having the game working and playing as it should. You don't HAVE TO restore the cabinet, backglass or playfield UNLESS there is a necessity. An example would be a flaking backglass. This needs to be addressed to arrest further deterioration. A cabinet being held together by the legs - again - HAS to be looked at. Each game is different, and each collector has different expectations. I'm a perfectionist, but I NEVER EVER comment on another collector's game, as it is not my machine. If I see the wrong rubber, or the wrong legs for the game - that's HIS machine, and HE likes it that way.
I used to think restorers should do their restorations according to a certain "code", or a "standard". But that was wrong. In clay's EM restoration guides, he repaints only the front door of some of his Woodrails - I thought that was lazy - but that's the way he liked to do them. That's his prerogative. He enjoyed seeing the front of all his machines lined up. It is just a different interpretation of a restoration. Like every machine, everyone is different in their approach to a restoration, and the criteria that dictate the requirement for the restoration.
What you do - whatever makes you feel good. It is your game, and there is no "right" or "wrong" way of doing it. It is a completely personal decision. I like the challenge, so I'll do everything I can.