I guess it applies to any form of Machinery or antique.
I belong to a few Auto forums and its always 50/50 For and against restoration.

Any vintage machine that will be put into service, will require some form of restoration to ensure its operable and safe.
And Machines kept purely for show might require cosmetic enhancements or nothing at all, so as to ensure perfect originality.

Rarity is also a contributing factor.
My preference personally, is Original over full restorations.

My general RULES of THUMB are...

- If at least 30% of the original paint remains, it has a nice Patina or any decals,then it
will be kept as original as possible cosmetically with minor enhancements and preservatives.
All mechanicals will be reconditioned or renewed.

- If its a good working original, it will be cleaned seviced then left alone.

- A wreck, incomplete or relic will be saved and restored to as-new condition.

Everyone has a preference, but I think mostly the scales tip favourably toward originality.