I have underquilts from UK Hammocks, Warbonnet, Wilderness Logics and Hammock Gear. Of those, I prefer the Hammock Gear underquilts. Yes, Hammock Gear has communication problems. And there were some issues with one of the underquilts I ordered 3 years ago (they forgot to sew on some tabs). But I recently ordered 2 short Incubators, one 20° and 0°, and they're beautiful. Very light. They fit my hammocks better than any other underquilt I own. The new suspension system is genius and much easier to adjust than any of the other full-length underquilts I used. And the Argon fabric seems to be indeed *very* down proof.
The other underquilts are absolutely fine to use, too. But I'm missing the ease of set-up (I needed to add lots of additional shock cords to keep the full-length uq from sagging). They are not cut to conform to the hammock/me as well. They are a lot heavier (with the exception of the Warbonnet Yeti and Lynx - but they are in a class of their own). And especially the Wilderness Logics uq leaks down.
Hammock Gear offers a lot of unique features that make their underquilts my first choice. Although if I were to use a 3/4 uq, I would probably go with the WB Yeti.