Re: What makes Piezo bridge pickups sound so great?
To me, piezos transfer very little of the character of the actual guitar, so the question becomes what do you do with the signal?
Take practically any unpreamped piezo straight into the board and you have one weak sound.
Use that same element, get it into a a high quality onboard preamp add high quality effects and you can get a sound that is as good as a similarly effected miced acoustic (of course a clean micd acoustic will beat a clean peizo unless there's some modeling going on).
In my experience, other than signal chain, the only physical aspect that influences piezo sound is string gauge- put a nice piezo setup and and run light strings and it will be far less convincing than a set of 12s.