From what I've learned about the both, mechanical is the way to go for certain types and electrical for others.
IMO It's easier to hookup the following guages mechanical than electrically, all you need to do is install the sensor/probe into an existing bung or create one.
Mechanical:
Boost
Water temp
Tranny temp
Oil pressure
Here is a good way to look at it, Mechanical gauges use a calibrated set of measuring devices to give you your reading. Example the mechanical boost gauge is going to show you an exact reading of PSI or (mm of Hg) reading as boost levels rise and fall in your intake. An electrical gauge basically uses the guts of a mechanical sensor with an electric gauge.
From what I learned working with SCUBA equipment and VERY high pressures and temperatures while compressing gases, mechanical is the way to go, you don't need a power source to get your reading, it's (almost) always going to work so long as your engine is running.
Last edited by Shadowlightning : 06-10-2007 at 09:52 AM.