I also recommend SR. While I'm not familiar with KLM's service, CO would also be a good choice, especially if they fly a 777 on the transatlantic leg. AF is inferior to SR, but not bad.
You may also wish to consider the departure/arrival times and lengths of connecting flights for your personal preferences, as for example long transatlantic (SFO-ZRH) with a short connection versus two more equal legs (SFO-EWR-AMS), etc.