Thanks for the input and also private emails on this
subject...
I would offer this as sort of a summary from what I
have read, far from it for me to be any sort of expert,
just my two cents.
It appears most pilots using either device are experienced
at thermalling...so these devices are used to aid,
rather then driving the effort. In particular the
idea to keep eyes-out of the cockpit, obviously (I
think) the idea of using these in a gaggle is unwise.
Other gliders make better indicators of the core.
As far a cost and logistics...one is just an upgrade
of software. So those already running WinPilot probably
have the less-painless option.
However, it appears the THEMI device is also an IGC
approved logger...so if true this may give an option
for non-Winpilot types.
I will wait and watch how these products are used,
if I wait long enough, I can usually upgrade my panel
using the leftovers from the 1V5 mob