One other thing I would suggest if you are shopping for avionics is how well does the stuff you are considering phase into the ADS-B 2020 mandate coming in only 3 years. Don't know about the others (except Garmin) but my Dynon Skyview system has been great for upgrading to ADS-B 2020. To be fully compliant with ADS-B (Out) all I had to do was install a replacement GPS antenna (identical mounting holes and dimensions & identical wiring); the Dynon transponder I already had was mode S and required no changes. Last week I went the other step and installed the Dynon ADS-B (In) module. My Skyview system was already set up to handle it and all I had to do was mount a very small black box and one new antenna (similar to a transponder antenna) and connect 4 wires plus one antenna coax cable. For both these ADS-B in & out installations nothing had to be done as far as new cutouts or holes on my panel face; all the new information reads out and is controlled on my existing Skyview screen.

As you can tell I am very pleased with the Dynon system and with only a couple days of easy work I am now fully compatible with the ADS-B 2020 mandatory (Out) and the optional (In). In-cockpit weather and traffic on a screen you can actually read in bright sunlight running on ship's power rather than batteries is really great. I'm sure there are other systems that are similarly good, but I wanted to relate my recent personal experience.