1. Webstones current kit is junk. Valves are always stuck and they tend to leak in weird places. THe unions also can be problematic. I no longer use them.
2. Simbario is a good kit but can have the same problem with the tiny handles sticking, like all the others with small handle valves. I give it a 8.
3. Brass craft...yuck. Looks like it was made in a garage. Give it a 3.
4. Jomar - Full handle valves best unions going and compact. I give it a 9. IT would get a 10 if it had separate valves for the flush port. THey use a 3-way ball to change flow directions for the flush port.
5. THe kits offered by the tankless mfg'ers other than Webstones are pretty much similar. Small handle valves I don't like adn quality varies. Probably a 4-7 for me.
So for me it's easy...JOMAR!