Before I left the DTW base I noticed that there seemed to be a lot of 737s over-nighting there. I'm sure there is a strong case for basing some there. I don't know enough about the 737 and A320 to argue why one is significantly different than the other. I think one of the most significant differences is that the 320's don't have seat-back entertainment, so I guess the 737 would be favored on longer flights because of that.