I will try to keep my opinion as unbiased ( if this is possible) as I can!
I have had the experience of working for 2 low cost carriers, before becoming a pilot for DAL (one of the happiest and proudest days of my life). Obviously most passengers rate their carriers by the meals, beverages and in-flight service they receive,(which I guess is part of it). May I offer a different insight in making your selection/rating a little easier!
There are many aspects of an Airline Operation that most passengers fail to consider. A carrier the size of DL, UA, AA, and a few others, has such a huge support structure backing up a flight, no small carrier can ever match. And remember, I am talking from personal experience. The level of safety that I have observed flying for DL is unbelievable, something that only companies with big pockets can offer. The route structure, options to the passengers, just to name a couple cannot be matched easily. Most smaller carriers do not have the fleet or flexibility, or maintenance outstations to either replace or repair an a/c and get the folks going on their way. There is also a lot to be said about the training of not only the pilots, but the flight attendants, maintenance, and various ground staff. The training facility in Atlanta is an awe inspiring experience, and Delta spends money in training. Believe me, training makes a difference. Not to mention the amazing resources available to the pilot inflight to directly communicate to a myriad of experts in real time for advice and guidance when something abnormal occurs. A visit to the Operations Control Center in Atl ( see NASA's Houston control), leaves the observer amazed!
Please do not mistake my small input here as an attempt to belittle the smaller carriers, or by any means say that they are not safe, this is not my intention or my belief. It is just that having been on both sides of the fence, DL is much safer, stuctured and organized than most smaller outfits will ever even dream of being!
The bottom line folks is, you get what you pay for, DL invests the bulk of it's money in maintenance, training and support. True, there is always room for improvement, but when you compete with low fare carriers, you have to cut something, and I'd rather have peanuts any day instead of overworked and underpaid employees!
I feel that this post will draw a lot of bad feelings from a lot of folks, just remember, this is an insider's point of view, and nothing else!