Originally Posted by tjl

Depending on where you'll want to use status perks and awards, see which FF program allows you to make the best use of status perks and awards on flights you are planning to use them on.

Regardless of how you book your Northwest flights (with Northwest, or as a codeshare from Delta if offered), you should be able to designate either a Northwest or Delta FF program for the miles.

Be aware that is US Airways actually does acquire Delta, there is a possibility of Delta's FF alliance / partnerships changing.