As for the complexity issue, I love the quote from J.L.K. Setright (a car magazine writer), that "Mercedes would never use one part where two parts would do."
As for the vacuum door locks, I have enough trouble and expense from repairing them as they age that I would much rather tolerate the slight noise of electric locks. And as for reliability, I have had a damn sight more vacuum door lock failures than battery failures. (I have never heard of anyone with electric locks having to repair them. From my 35 years of MB experience, vacuum is more likely to leak from old brittle tubing and fittings than electrons are to leak from decently made wire.) Plus, my two W124 sedans have both had lock failure modes in which the lock's vacuum pump keeps running after the car is shut off, keeping the locks shut so you cannot get into or out of the car without overpowering 9and probably damaging) the locks. Now THAT is a royal PIA.

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DavidB29
1992 300E with ASR
35 years of Diesels until now!