I'm looking at a few open jaw flights from SFO > CPH, then CDG > SFO, and there are AF/Delta, KLM/AF and Lufthansa/United flights. Anything to consider when choosing between these (besides price)?

The SFO > CPH will have a layover, and depending on the flights, the layover is either in FRA, AMS or JFK. Is a Europe layover more ideal than JFK?

Flights from Paris > SFO will be nonstop.

Will likely fly premium economy but also want to consider differences between premium economy and business between the carriers.
Thanks!