When Auburn plugs were available we used to use them
exclusively. They lasted much longer than the Champs. Then Champion
bought them up and shut them down. We'd formerly had a lot of trouble
with Champions failing the testing at 50 or 100 hours, and it seemed to
be the spring-loaded internal resistor that somehow lost its contact,
even though I could see nothing wrong with it in any plug that wouldn't
spark. I'd even had Champions failing right out of the box.
We started using the Unisons when they came out. They had the
same monolithic (molded-in) resistor the Auburns had used, and worked
well. In the last year we've had trouble with them misfiring, and on
the test stand they will arc in the cigarette barrel; the spark would
rather jump from the contact button to the shell rather than across the
gap at 120 psi. I think it's another resistor problem.
Misfiring plugs aren't always readily apparent. You might feel
the slightest bit of roughness, usually in climb or leaned cruise, and
if the mags aren't timed exactly together. As the earlier plug fires
and the cylinder pressures start to rise, the other can't or won't fire
and you have a slower burn in that cylinder. Switching from BOTH to
LEFT or RIGHT won't detect anything.
We're using both Champs and Unisons right now to see what the
eventual outcome might be.

Dan