Well, i don't think there's anything wrong with mechanical--they may even be more accurate. But the way i look at it, you have to wire them for lights anyways, unless you only drive during the daytime. So, why not just go electrical all the way? i also believe they are easier to install than mechanical because you can route the wires anywhere you want. (You can probably tell i generally favor electrical over mechanical.)
As far as monitoring, if you can afford all those gauges then great. i would first and foremost want tach and water temp. Then oil pressure, i don't give a crap about oil temp, but pressure yes. i've drifted towards, and gotten comfortable with, voltmeters----probably because that's what the factory does, but maybe we need both---an ammeter AND voltmeter to see not only how much is staying in, but how much is going in.
i would also recommend adding a "dummy light" to each of the gauges----this way you can shut it off immediately at the first sign of a problem. Otherwise, you could be cruising for miles before you notice something wrong.