So I've ended up signing up for Delta SkyMiles because a different trip I am taking to Europe on them should help earn miles. I decided that with the miles transferring between Delta, Virgin, KLM, and AF that it was going to be plenty useful, and the miles from the earlier trip would likely outweigh any advantages the other programs were offering.

Thanks for the help everyone, and I look forward to many exciting trip reports and travel stories in the near future.