I have the GRT EIS for engine monitoring and the older Sport system for flight instruments. It has worked just fine and never given me any trouble. I have had the EIS engine monitors on my last 3 planes and like them very much. That said, the Dynon stuff is good gear as well, and if i was buying today I would seriously consider buying from Dynon. One thing I like is that they seem very simple to setup and have a few less features (which I think is a good thing). You can't go wrong with either as they both have good support and lots of field experience.