As far as FF goes, over 5 years I was upgraded to FC 99% of the time on NW, So I was never worried about coach seating. There are so many additonal bonus programs for miles and free flights than when I was with UA.

If your living in Michigan, Id go with NW/DL. I use to fly UA out of AZO and got tired of driving from ORD when I couldnt get home on a flight for various reasons. It so much faster for me to drive from DTW than from ORD -and its about the same distance.

Being in Kalamazoo area I have choice of GRR,AZO,LAN,and SBN all within an hour or less. Better chocies to get the best price. If I got stuck in Detroit trying to get to one of the above airports, I could just fly to one of the others and get a OW rental home.

Delta has made changes to its program that PO'd prior customers, but Im not sure if thats been good enough as Ive not looked at all the changes.