I'd go with NW. I have all three programs (for many years before they were partners) and NW has the most flexibility in award redemption and a good network esp with the new alliances and soon-to-be Skyteam member.

I've been so happy with them that I've kept most of my miles with NW and now GOLD with them.

They have good "bonus" options, including new member referral bonuses for the person referring and the person being referred. (I'd be happy to refer you if you don't have another person).

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