Out of four different transponder and encoder combinations I've used
in gliders (Garmin/TransCal, Terra/Terra, 2x Becker/ACK, 2x Trig) the
Trig has proven to have the least power consumption.
The Trig is easy to install if you buy your own D-Sub connectors or
a crimp tool for the included ones, or have someone with a crimp tool
build the harness for you.
The small Trig control panel may fit in a corner of the panel you
thought unusable.
RG58 antenna cable worked fine for me (even with a TNC to BNC
adapter), but total cable length is less than 10' / 3m. For longer
runs you'll do better with something lower loss.
Joshua and Oakland have had no trouble getting radar contact with
the Trigs.
At the three avionics shops I called about Mode S, cost was the same
to certify Mode C or S transponders.
I believe the Trig takes less time if any adjustments are needed, but
in my experience they haven't required adjustment. The altimeter is
the most likely thing to require adjustment.
And it's Scottish, so it can't be crap!
Jim