In my opinion Sunday. First of all here in the bible belt 60% of the clubs are closed. Of those that are open, they don't open until much later. 4PM or later and I am a day shift kind of guy.
None of my favorite dancers work on Sundays. Seems like the only ones that do work are the fuglies that didn't make any money on Fri & Sat. I also think that a lot of girls are just taking the day off to rest. Of course they could be going to church. LOL.
Anyway I avoid Sundays.

Monday seems an off day to me. Even so, I don't avoid it. I go when the money, time, and place meet, no matter the day.