Accuracy is determined in the calibration and the quality of the gauge. A mechanical gauge will always react faster (So long as things that would slow it down are removed such as a weak rubber line to it being replaced wtih a silicone and the like) because there is no time used on being read by a sender, then the signal sent, then the signal received and displayed. But on the flipside, most of these mechanical gauge are lower quality than the electrical ones meaning they are less accurate. If I had the money, I'd go Defi but I don't know what I'll end up doing, I have a problem with $1000 for gauges.

-Andy