As Adam's answer indicates, there really is not much difference between
almost all of the domestic first class seats on the various airlines.

The only really nice domestic seats are in the various airlines' business and/or first seats between JFK and either SFO or LAX. But such a routing would mean you'd need to take three flights to get from PIT to LAS and probably be considerably more expensive than a more direct route.

Of the various options JFK-SFO/LAX options, I believe that the new JetBlue business class (or whatever they are calling that section of their planes) between JFK and SFO/LAX might be the least expensive right now. I believe they launch the JFK-LAX in January and JFK-SFO in the spring. But then again you'd have to connect to the JetBlue planes from other airlines.