Take Sun Country!!!!
A BRAND NEW 737-800.
Although, I love DC-10s, and I would probably take that one.
You may never have another opportunity to fly a DC-10. I won't. I live in Dallas, and I attended the final arrival of an American DC-10 last fall. I wish I had the chance.
As far as service goes, the consensus of THIS FORUM seems to be that Northwest's service is lacking. Little in flight entertainment, if any, and pretty boring overall.
However, people here seem to be growing to hate Delta with a passion. I hear lots of complaints about CRAMPED coach seating and less than cushy first class on the 764.
Are you limited to DL or NW?? I might consider United. I like United, and they have great service in my experience from March and May.
Also, Atlanta is a terrible airport. I don't like it at all. That's my honest opinion. The terminal is HUGE and the transportation system is impossible to find.
That's everything I can suggest about this.