I fly IAH-AMS at least twice a year...

KLM is the best way to go if price is an issue, their economy is the best of ST.

I fly CO if by myself with a 40k point charge to get into BF at a price of 2.3k.

Trust me BF is far better than Economy on International flights. I could list reasons but I would get banned LOL.

AMS has passport control so pay heed to your connecting flight time. Passport control usually has long lines.

By the way if you have a PCard, you can get into the KLM Lounge which is pretty nice (complete with a smoking lounge).