Michael,

I had the Ryan 9900BX TAS (which became the Avidyne system when they
purchased Ryan) installed in my Cirrus SR-22.  I don't have any "hard"
performance data.  However, after several years of use, the system appears
to reliably identify aircraft within the parameters (i.e., limits)
established by the unit's software.  Range information (measured by
transponder response delay) appears accurate.  Azimuth data is subject to
vagaries of antenna patterns; sometimes a target will "move" around a bit.
However, it appears surprisingly accurate.

I have no comparative data to offer.  Sorry!

By the way, the TAS isn't perfect!  I have seen "holes" in the coverage
where an aircraft will suddenly appear out of nowhere on my MFD (and Garmin
430s).  However, this particular phenomenon rarely happens.  As an
electrical engineer, I suspect that it's due to the antenna patterns that
develop the azimuth info.  As a pilot, I'm content with its performance.

Side note:  If you're in the pattern at a busy airport, the traffic warnings
can drive you nuts. <grin>

Craig
 
Craig Albright, Flight Instructor
Gossamer Wings Aviation
Gilbert, AZ
480-776-9358 (c)