On all but the widebodies, the FOs at Delta are making less than the senior ASA/CMR/Skywest.

Wrong again Joe!!! I was an 8 year guy at skywest. 400 outta 2700 when I left. I make the same in year two at Delta flying narrow bodies. I will make substantially more in year three. Upside pay potential at mainline ... stagnation at the commuters. Also have 16-17 days off just like the commuters. Oh, and a much larger contribution to my retirement. I will concede that job security as a junior guy was my main sticking point coming to a carrier just out of bankruptcy. A nice California base was also difficult to leave. Your pay argument will never cut it though.