Purely informal, to each their own, QOL is more important than money for some, money is for others.
All from APC pay rates:

year: Spirit/UAL/%

FO
1: $38/$79/48%
2:$72/$122/59%
3: $78/$142/54%
4: $84/$146/57%
5:$90/$149/60%

CA
4: $131/$231/56%
5: $136/$233/58%
6: $142/$235/60%
7: $147/$237/62%
8: $151/$238/63%

Top out year 15 for spirit, year 12 for UAL
FO: $109/$168/65%
CA: $185/$246/75%

*This doesn't include the upcoming pay raises for United

This also doesn't reflect the fact that there are captains at spirit and F9 that have only been on property for 2-3 years. So pay rates come close to evening out. It also doesn't reflect that upgrade times at the big 3 are coming down and already have significantly at AA and DAL with UAL not far behind given current projections.