When I was setting my plan, the GRT was in the running. To do their flight and engine instrument, it required the installation of their EIS box as well as the flight instrument box. I asked the rep at OSH if both were needed, because the flight box also displays the engine info, I was told yes. The EIS box drives the other box.
I was told I could just bury the EIS box behind the panel and not display it. I didn't like that idea for the room it took as well as the wiring complexity. Not to mention buying an EIS box, then hiding it.
The Dynon was all in one box and seemed easier to install/wire.