Delves for Farming (Switch)

Thinking of the 4 Delves available on Switch (All-Seeing Eye, Hall of Guardians, Crypt Keepers, Sea of Sorrow):
Which one is considered being the best for farming? Is there a common sense?

I kept ASE and SoS low and am now thinking of leveling one up.

Of all delves, ASE is by far the worst delve for farming. Simply because it has only 8 rooms, while all other has 9.
Of the delves which you mentioned, Sea of Sorrow is the best for farming. However, relatively soon (after Primal Rift and The Warrens) you will get Fang Moor which is better than SoS. Then, after Dark Pits, you will get Silver Necropolis which is currently the best.


This is OT but If I may ask, which underground city was the one some players have expressed regret of going deeper than 20th lvl?