Electric Gauges VS. Mechanical Gauges

[smp3000]

Ok, Ok,

I might be off my rocker asking this question but I can't seem to find answers elsewhere. Last night I ordered a greddy electronic boost gauge, and a greddy electronic EGT gauge.

While searching I noticed that each company had electronic AND mechanical gauges. The mechanical ones were much much cheaper. What is the difference in these. The pictures seem to look the same. Is it a difference in how the operate? :wtf:

 

[1sty]

From my brief talks with Spoolin I have gathered that the air/fuel gauge must be electronic or you would have to run a fuel line into the car or mount it outside the Corky suppies is mechanical but is used to setup only nit to permentanatly mount.