LON is tougher but the damage output is lower, even with Zuni using Unity.
With increasing Grift levels the monster health grows much faster than their damage output.
So initially in the season LON is popular because defense is a limiting factor, and as ppl get more paragon and augments (and a 3rd gem at higher level), Zuni will take over as damage output becomes limiting.
Right now Zuni gets me about 2 levels higher.
How to cope with the squishiness of Zuni ? I’ve dropped Soul Harvest for Horrify so I can keep at a distance all the time, and changed PTV (which is really only about 11% dps because of all the other DiBS) to Bad Medicine.