Top Domestic Contenders:

Seat 1K First-Suite UA 763 (international configuration)
Example:
UA 972 SFO 10:11 AM --> ORD 4:24 PM
UA 907 ORD 5:15 PM --> SFO 7:57 PM

and

Seat 1A First-Suite AA 777
Example:
AA 299 MIA 8:40 AM LAX --> 10:50 AM LAX
AA 1520 LAX 12:05 PM --> MIA 8:10 PM

The UA 763 suite wins because of better IFE screen and options.

CO 757-200 Seats are great - but do not compete with modern first suites. The first suite offers much more personal space and privacy.

Of course the Cathay First Class Suite (eg JFK-YVR) is better if CX is allowed as a contestant.