I have a very precise balancer that is made from MAP sensors outputting to an Arduino and displaying on a screen with a bar graph and numbers. The resolution is far better than an electronic LED device or tube type gauges.
Because I built it I have been using it a lot, not because I have engine problems but I am more testing the tool, and I wondered how well the carbs stay in balance.
I have tested it 3 times in the past 50 hours of flight, zero change. One time I removed both carbs from their boots and changed bowl gaskets, still no change.