I do not have direct experience with the Wing Rigger. I have been
using the Cobra one man rigger with a Grob Speed Astir, an LS-8-18,
and an SZD-59 with total karmic harmony. I prefer using a one man
rigger for many of the previously discussed reasons: less damage to
plane from assistant's good intentions, more time to lube pins and
fittings since another person is not risking a hernia while holding
the wing, more freedom at the soaring site because I don't need
another person to rig or de-rig.

I use the Cobra system on gravel, dirt, and pavement. Works very well
in all situations. I have watched other people use the Wing RIgger
and have to say that i prefer the manual crank for elevation control
that the Cobra has over the gas spring system in the Wing RIgger.
However, that is only a matter of taste. Both work great.

Guy