Used a friend's $3500 vaccuum/pressure gauge tapped into the same place as the boost gauges, plus the reading from the UTEC. I'm not sure the brand, but it's for industrial/military applications, and from what I've heard it's among the most accurate pressure gauges in existence.
The facts speak for themselves. The electronic ones were all within .1 psi of each other, and within .1 psi of both the UTEC and the pressure gauge. The mechanical ones were not. In fact, all read lower than actual pressure. Some as much as 2 psi lower.
But, you seem convinced that I'm wrong, so buy whatever you want for your car. I'll stick with electronic gauges on my car.