After a lot of domestic flying, it looks like I am going to have to fly to AMS for work next month. I am new to international travel. I have two questions that may be silly to experienced international travelers:

1) Which airline is better to take? CO, or NW/KLM? Both offer non-stops on this route.

2) I am OnePass Gold. As a Gold, what are my chances of getting an upgrade on this flight?

Thanks in advance!