In almost a million miles of driving MB cars with vacuum actuated system locks, I have replaced two diaphragms, one on a drivers door and one on a fuel tank flap at a cost of less than $10 each.
The vacuum system is simple, effective, economical and trouble free. I think your luck has been very bad. Additionally, I would bet that I could fix any one of those cars for $10 worth of parts or less.
To answer your question, my 2001 C240 has electric locks. I consider this to be a step backwards.
Also, my daughters Honda has electric locks. This car is two months old and has been at the dealership almost three weeks supposedly awaiting an ECU that has been on order all that time. Japanese cars are mostly crap and just because they have electric locks does not mean that electric locks are superior. If it's on a Japanese car it's probably on there because it's cheap.
Have a great day,