The biggest difference in performance between electronic and mechanical is durability and functions. Electronic gauges often have features such as warning lights, max boost memory, boost level playback, digital recalibration, etc. They are also more responsive and slightly more accurate. Accuracy and responsiveness between a GOOD mechanical and an electronic is negligble, but exists.

Also, mechanical gauges are usually built to be less durable. Since the sensor itself is mounted internally in the gauge, as opposed to near the source, manufacturers don't build them to take as much abuse. As such, hard riding cars and vibration tend to affect mechanical gauges more.

Electronic gauges offer greater customization by allowing you to mount anywhere between the source and the gauge. They are also built to withstand greater stresses. And if you mount closer to the source, you will get a more accurate and more responsive gauge.

There are other differences, but I believe those were discussed in the original post.