Others may see it differently, but given the similarity in domestic F offerings, I think the airline that does it better on this route is the one that does it cheaper. No idea when you're flying, but I plugged some dates in September into ita and see there are many round trips on Delta at $631. I don't think you'll see prices much lower. Buying the ticket at a price like that is probably a better deal than trying to upgrade, if you have no elite status and would have to pay a copay in addition to using miles, all to go on a waitlist that may not clear.