I like a mechanical one if it fits your application.
I think that they are simple and very trouble free.
I think electric ones take a simple job and complicate it. With mechanical if the engine turns it pumps, there are only two check valves and a diaphragm, if it does not work it is easy to troubleshoot.
I have never had a problem with a mechanical fuel pump when using good gas and a filter before it.
I have never used an electric one, so my opinion is one sided.
I would only consider an electric one if the mechanical could not deliver the required amount of fuel or pressure.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-