I fly into LAX every Sunday and out every Thursday (unfortunately, not for trips to DL), and yes LAX is/can be a pain, but it really depends on a lot of variables. The time you fly in and out being the biggest factor. Sunday evenings, Monday mornings and Fridays are the worst as you are competing with business travelers. Summer is much worse for obvious reasons. The airline you fly is also another variable. Some are better at getting your checked luggage down to baggage claim while others you will wait literally an hour! Traffic in and around the airport is horrible, especially at the times that I've listed above, if you are renting a car all of the agencies are off-site and you will have to take a shuttle to get to the lots. If you plan you can make this really work to your advantage, I can get in and out of the airport in 15 minutes (I don't have checked luggage). Driving to DL is fairly easy, but be sure to have a few routes because traffic can be horrible and you could potentially sit on the freeway for a very long time (I suggest staying off the 405 and heading south)
As far as SNA is concerned, I have found it to be more expensive and the flight times aren't always convenient. But, it is the closest, it is easy to get in and out of, luggage is a breeze etc etc etc. The one thing about SNA is the take off - if you have not done it, it is quite different because of the noise abatement in Orange County. Most good pilots will warn you of this, because it is a very odd feeling; however I have been on flights where they have not and people freak out on the plane.
I cannot comment on LB as I've never flown, and the same for Ontario; however I don't feel comfortable in Ontario and so I don't believe I would recomend it for that reason. Burbank is small and great airport- but it is quite far, distance wise and probably time wise; however DL would be a straight shot down the 5. If I could fly into Burbank I would in a heartbeat, but flight times are inconvenient...
Regardless any of the airports are relatively close....in LA terms