So your JFK-SFO will be United's Premium Service. First Class is almost lie flat and has from what I understand quite upgraded service from domestic first class. However, with the merger, many are complaining about First on PS losing its magic, right as Delta's Transcon Premium Product is getting quite good. Nevertheless, it is sure to be better than regular domestic first or business. Your trip on the way back will be a BusinessFirst seat and Domestic First Service. You can look online to get details on your meal options. The BF seat is completely lie-flat, however you only get BF on this aircraft because United is optimizing their aircraft routing and using an international plane for this route. This is not sold as a BusinessFirst market.
So, in conclusion, if you want something special from NY-SFO go to JFK and take Delta's BusinessElite or United PS. Also, I think American has something for that route. But if you just want the seat go for EWR-SFO on the UA 752, it'll be better than the options from JFK. And the service will be regular domestic first.