The quick upgrades at AA are on the 190 in PHL.

The quick upgrades (5 yrs I think?) at UAL are in SFO and EWR 737 and 320.

The quick upgrades at DL are on the MD-88, 717 and C-Series (maybe the 320/737?).

Good if you live in those bases and want the extra pay. I wouldn’t commute to a garbage schedule just for some more pay.

Choices are what those airlines offer. Choice of fleet gives you different routes, etc.