What are the best una tasks for solars?

At a certain point, doing solars will be more valuable than doing shards.

Considering we will have a lot of shards over time, solars can significantly cut the cost of the honing. Especially on weapon, likely after 17+ ( didn´t do the math, so maybe even 16).

I am not the math andy, but it certainly seems like a viable thing.

And if you are mega el cheapo rat on some of your chaos dungeon alt that you are Sometimes consider pushing a bit ( maybe if some express or something pops up), then you are not doing your unas on them. But if you were to do solars, now that could cut the costs of honing in a decent manner. Even if it´s just rested unas.

Thus i wonder if anyone knows, which are the quickest unas.