Worth it is relative
Worth it? If I had just enough miles or one cert to UG, I would do SFO-NRT over SFO-JFK if I couldn't afford to pay for C. So, only OP can make the "worth it" determination.
To me, I could care less about the food, it's comfort and on a red eye, flying in F/C makes all of the difference. I fly C on this route and will UG to F if it's avail. whatever the time of day. If you want something more substantial than UA offers, there's tons of good food at SFO to bring with you.