With such a low difference it's a no brainer, take AF. You won't have to pay for all the basic services including a blanket. In case of irrops, good luck with Norwegian.
But there is something I don't understand in your post : you say it is Paris to SFO and D8 arrives at night and AF the following day ?? This is not possible. In that direction, both flights are day flights. And D8 doesn't fly to SFO but to OAK.