Well, in my area (CLE), like yours, it's not really a fair question.

I started leaving CO when they eliminated CAK-CLE service, and started replacing mainline service with ExpressJets in major markets. I'm good for about 90 minutes on any commuter plane of any kind, and when commuters started popping up to ORD, MDW, LGA, etc... I realized that I needed to pass thru a bigger hub to be on bigger airplanes. I still fly CO on occassion, but it has to be mainline nonstops from CLE. I'll fly 'em to Vegas for Labor Day. If all things were equal? Here's the scorecard:

Fares = slight edge to NW, but I never buy full Y

People = NW has made big improvement, but front line at CO is still better

Destinations = NW. I can't get to PDX or SEA on CO unless I go to IAH. NW's NRT hub gets me to TPE, and the NW/KL alliance is much more comprehensive for Europe.

Clubs = I love the look of the new WorldClubs, but I miss the Kirin! I don't miss the bartender in the NW clubs. The lockers with charging stations are a nice touch too.

Equipment = NW, because they fly full size jets into more locations. And there's still nothing like a 747-400!

Upgrade ability = NW. Automated upgrades are much easier to come by on NW. For myself as a plat, it's a wash. But for my wife (silver), NW always comes thru without A9 F0 shenanigans. Anytime I've needed to upgrade an M fare to Asia, it's never been the hassle CO makes it with HoKeY.

Overall = NW. As recently as last summer, it went the other way. I had some real problems with NW last spring, during the mechanics negotiations.

It just seems that NW wants my business these days. CO just seems to want to figure out how to get more money out of me. It doesn't mean that it couldn't swing back, but I don't see it happening any time soon.