... pulling up the numbers from the 2021 annual reports
F9
CASM 8.10
RASM 7.67
UAL
CASM 14.36
PRASM 11.30 (passenger RASM)
TRASM 13.79 (total RASM)

I'd use UAL's PRASM, but they also have quite a bit of cargo revenues which is why the TRASM is 2 1/2 cents higher than PRASM. I couldn't find any cargo revenues in F9's annual report.
Both F9 and UAL are losing money on every seat mile flown, but F9 did a bit better than UAL in 2021 (.14 cents better per ASM)

I expect UAL's CASM to fall a bit in 2022 due to cuts in express flying. UAL didn't break out express numbers, but in previous filings, express CASM was considerably higher than mainline CASM.

RASM for both airlines should rise in 2022. UAL has the advantage of international markets opening up and a marked increase in business travel (based on what Delta stated in their Q1 earnings release). From Delta's earnings release:
Business travel recovery boosted by improvement in corporate: Domestic corporate sales* for the quarter were ~50 percent recovered, with March improving to ~70 percent versus 2019. International corporate sales for the quarter were ~35 percent recovered, with March improving to ~50 percent versus 2019. Internationally, Transatlantic improved the most as European countries reopened.
• Premium cabin revenue recovery outpacing Main Cabin: Premium products continued to lead the recovery with Domestic premium revenue approximately 100 percent restored to 2019 levels in the month of March. Domestic and Latin premium product revenue recovery outpaced Main Cabin by approximately 10 points during the March quarter.

Neither F9 nor UAL have posted Q1 earnings yet.

As another RASM comparison, in 2019, F9 had a RASM of 8.92 and UAL had a TRASM of 15.18 (PRASM of 13.90)

Yes, F9 has a considerably lower CASM. But they also have a significantly lower RASM.
I could post that UAL's RASM is almost twice as much as F9's RASM, but it doesn't tell the full story. Same for just talking about CASM.