Dave you are not comparing like for like.
If a punter had a choice between a car with service stamps from a main dealer or a car that the owner simply serviced himself - and had receipts for consumables - most would ptefer the former, all other things being equal.
If however you are comparing a car with service stamps to a car that has been partly disassembled by an enthusiast owner with previous experience (you for example) that has meticulously cleaned, restored or replaced everything that needed it to a proper standard and documented all of it with lots of photos then a prospective purchaser may well prefer the latter.
I would add that a really skilled amateur mechanic with experience of these cars can also spot and rectify most if not all of the issues a specialist professional can (I suspect Lithospian is such a chap, so is Martin R) but how would a prospective purchaser know who knows their shit and who doesn't?