If you absoloutly, beyond the shadow of a doubt, need to kow EXACTLY what temp/pressure you are reading, then go mechanical. And as stated above, only use copper line. The vinyl line that comes with the gauges is crap and will break when it gets too hot/cold/rubbin' up against something! For a daily driver/mostly street vehicle though, I like a good quality electric gauge. No mess in the interior if a line does leak at a fitting (and it will), and I'm really not concerned if I have 65 or 67 psi of oil pressure. IMHO you can not buy a better gauge, mechanical or electric, than Auto Meter.
1983 CJ-7 Laredo