After flying from MSY-ORD three times in the past few months, in first class each time, I thought it might be interesting to perform a quick comparison. United is my airline of choice, although for various reasons I had to fly AA and NW as well.
On this particular route, my recommendation is to fly AA, but YMMV, of course. Overall, I favor United on a system-wide basis, but read on to see why this route really shows the differences between the airlines. Note that NW is actually MSY-DTW-ORD, but for comparison purposes, I'll evaluate MSY-DTW as it is almost the same length as MSY-ORD. At the end, I'll state where I think UA could stand to improve based on what the other carriers offer.
UA: MSY-ORD (evening departure, B737)
Check-in: At the first class desk with an actual agent. She was pleasant enough, but not especially friendly. Baggage was tagged with Priority stickers as this was part of an international itinerary. 8/10
Gate: Flight boarded on-time and efficiently. First Class was invited to board first, followed by elite, etc. 8/10
Pre-flight: Choice of OJ/water. Coats taken. 8/10
In-flight: FA was very attentive for the first half of flight, constantly refilling drinks, etc. Nuts were warmed.

Dinner was served, although it was a cold entree and not particularly good. For some reason, during the second half of the flight, the FA disappeared into the galley and service levels dropped off dramatically. 7/10
Seat/cabin: Seats were standard UA domestic FC seats. They are similar to the international BC seats and quite comfortable. The cabin was reasonably clean. 8/10
Entertainment: Only audio on this particular bird. Channel 9 was on, a big plus. Otherwise mediocre entertainment. No reading materials offered. 7/10
Overall: 82/100 (subjective, not a summary of above scores)
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AA: MSY-ORD (evening departure, MD-80)
Check-in: Initially with the self check-in machine, then to the FC agent to request an upgrade using some certificates I've had in my account for a long time and haven't used since I don't usually fly AA. She noted that I was not an elite member, but said that as a one-time thing, she would upgrade me anyway since I was nice. I was also on a mid-tier coach fare, if that meant anything. The agent asked me to fly AA more often, and was very professional both in attire and manner. 10/10
Gate: Flight was delayed by about an hour. The gate was serviced by two agents, which helped them to assist passengers more quickly. The agents made an announcement that we would board at 7 (original departure of 6:30) but that wheels-up time would more likely be around 7:30. She apologized for the delay and explained that it was due to air traffic control restrictions. Very professional and accountable. Once boarding began, at 7 as promised, First Class was invited to board first, followed by elite, etc. 9/10 (points off for delay, professionally-explained or not)
Pre-flight: Choice of any beverage on-board. Coats taken. The FA came around with magazines that she had collected from earlier flights and offered them, along with a request that they be returned along with any other reading material we'd like to donate once we were finished with it. Very nice pre-flight experience, especially given the delay. 10/10
In-flight: FA was very attentive. Lead FA came around and introduced herself, taking drink orders and meal orders. Choice of hot entrees was offered. Drinks were constantly refilled. No nuts were served, however, before dinner. Dinner itself was reasonably good, although the vegetables were overcooked. 9/10
Seat/cabin: Seats were standard AA domestic FC seats (new style). They are similar to the international BC seats and very firm and supportive. The cabin was immaculate. It was also half-empty, which helped create an aura of spaciousness and comfort. The lights were dimmed just before the meal service, so we ate with our reading lights on, which was nice because it enabled us to finish at our leisure and then relax/work in peaceful darkness. 10/10
Entertainment: No audio or video entertainment on this bird. The reading materials offered was a nice touch. 6/10
Overall: 96/100 (subjective, not a summary of above scores)
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NW: MSY-DTW (evening flight, DC9)
Check-in: At the first class desk with an actual agent. She was pleasant and friendly. Baggage was tagged with Priority stickers as per NW norms. 9/10
Gate: Flight boarded on-time and efficiently. Exit rows were invited to board first, per NW procedure, followed by First Class, then elite, etc. 9/10
Pre-flight: Choice of any beverage on-board. Coats taken. Was done very slowly though, which I've found tends to be the norm on DC9's owing to the small galley and forward entrance door. 8/10
In-flight: FA was reasonably attentive during the flight. Drinks were offered, but not refilled; I had to ask for more. A packet of pretzels and of mixed nuts was offered. Dinner was served with a choice of hot entrees. Reasonably good dinner, although salad was a bit wilted. One oddity: the FA plated the meal on the cart, instead of in the galley. My guess for the reason is the small galley on the plane. 8/10
Seat/cabin: Seats were standard NW domestic FC seats. The DC9 seats are not as comfortable as the ones on the A319/320, and the cabin is narrower. Frankly, UA E+ seats have as much legroom as NW's FC seats (around 34-35"), but not as much width or feeling of space, and NW FC offers legrests. So it's a definite step-up from E+, but not at the level of UA/AA FC seats. Cabin was clean. 8/10
Entertainment: No audio or video entertainment. No reading materials offered except for the not-very-good inflight magazine. 1/10
Overall: 88/100 (subjective, not a summary of above scores)
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United offers a decent FC product in this market, but it could improve in several ways:
-offer more FC seats. A two row cabin in domestic configuration just feels small and not very exclusive. The upside is that service is quick, but I'd rather a minimum of 12 FC seats on the 737. I suppose E+ is the substitute for that extra row of FC, but I'd like to have both!
-offer a choice of any beverage on-board prior to departure, not just the usual OJ/water, where time permits.
-offer a hot entree, and preferably, a choice of two.
-have reading materials onboard, although Hemispheres is easily better than American Way or NW's magazine.
I realize that an anecdotal sampling of routes is not necessarily indicative of an airline's overall service offerings. However, in the "short-haul offering a meal service" category, the MSY-ORD route is a very good sample, because there are two carriers offering meal services, and more if you include NW's flight to DTW (since DTW is so close to ORD) and possibly even CVG with Delta, although that's a little further than DTW. Also, the evening flights all leave around 6, which allows for nearly a full day's worth of work or sightseeing, and arrives between 8-10, allowing one to get to a hotel or home in reasonable time.
Has anyone flown MSY-ORD on the evening flight in FC more recently than I did (in August)? Has anything changed since my experience? That would certainly affect my rating of UA, so hopefully progress has been made.