I'm a huge fan of Delta. The price is right, the service I've received has always been great. I've booked online and through Delta Vacations, and have never had any complaints. I even double booked a vacation package due to internet problems, and they happily refunded my card and cleared the entire issue up. I've flown Delta quite regularly and have NEVER missed a connection, been dumped, had anything cancelled. I have no complaints.
Every airline appeals to different people for different reasons. Just find one you are comfortable with, and don't worry about the others. Most airline fares are comparable, so find the one you like and stick with it, then you will not be disappointed.
Just my opinion!