I'd disagree with name recognition. The Delta name is huge on the entire Eastern Seaboard - the name Delta is quite large in the Northeast - them and US Airways are the two huge players. NW is below US, DL, AA and CO in the Northeast.

Also, on the West Coast. Delta covers most of the West Coast via SLC - every major market, plus most secondary markets and many tertiary markets. They're pretty well known out there, especially compared to NW, who has 1-2x daily flights to MSP in many cases out of the secondary markets (SJC, SNA, SMF, etc.).

In the Rockies, DL has a slight edge, but NW is well known there due to MSP. In the Midwest, NW is much more well-known than DL.

Also, internationally. NW has the edge in the Pacific by a large margin. Delta has Latin/South America - NW flies to a few cities in Mexico that would have large Mexico-originating traffic, but many of its cities are vacation spots on the coast. DL's ATL hub has the whole Latin America market well covered - AA, DL and CO are the kings in that market; NW, US and UA all pretty much serve the vacation spots in this places. But for Europe - DL has the edge (although KLM is very well known there). Middle East/Africa - Delta has the edge (though this is an emerging market).