What do you think they use to calibrate elect guages??? Mech guages. I know from experience. Mech is better, but dont last as long. Once you calib a elec guage you never have to cal. it again. On Mech guages they become unreliable after a while.

Electrical guages give their readouts using variable resistance. They change resistance in the presence of more/less heat, sun, whatever they were designed to. The pressure readout at the guage inside your car is guaranteed to be less accurate than one that takes that measurement at the exact location and then simply reports that readout to a guage inside the car.
Electricals are better