I prefer mechanical over electrical.

As part of "urban camoflaging" I don't want an electronic screen where the cops will mistakenly think they see a "radar detector", or "TV viewer".

And .......I mount my gauges below the dash line to lessen it being seen.
When people put them on the window post, not only does it give them something to smack their face against in a crash, but the lights attract the
cops, who have seen buttheads on the street with window post gauges,
..........and they think "here's another one.....".-Bob