Also consider AA. They have a lot of SFO-JFK flights and upgrades might be easier than UA.
I personally think that UA ps (SFO-JFK) service is quite good and we were able to score upgrades on weekend travel even though no one travelling had elite status. All SFO-JFK flights on ps service have Economy Plus; I think AA also has MRTC on this route.
And B6 is no match for E+ even with the TV.