Welcome to FT, yyclady!

I lived in Amsterdam (AMS) for 3 years, and I ended up in Delta's FF program instead of KLM, for a few reasons:

1. For the cheaper flights, KLM would only credit 25% of the mileage, where Delta would credit 100%. This allowed me to achieve Pt status on Delta last year even though most of my flights were on KLM planes. Had I credited those miles to KLM, I'm not sure I'd have made silver.

2. With Gold status (or above) on Delta you get access to the flagship KLM lounges for all of your KLM flights you credit to Delta, since it's an "international flight" for Delta. It also gets you into the fast-lane for security on Schengen-Staten flights

3. This got me some occasional upgrades on the US segments of my trans-Atlantic flights. I also got lounge access back in the US from this.

4. Skymiles, while low in value, don't expire.

Honestly, I'd rather have miles in the star alliance if all other factors were equal. But with AMS being a Skyteam hub, Delta worked out the best for me.