I always get a bit frustrated about LGB and what I see/read. As a native Southern California, and being involved in
Disneyland and Theme Parks for decades, you see comments like John Wayne (aka Orange County/Santa Ana/SNA) is nice and small and so convenient, so close to Disneyland, etc.
Long Beach is the true small airport in the area, John Wayne is a medium sized airport that offers International Service, and then you have the very large LAX.
And as for distance, we can argue about which one is closer depending on how you measure, but I prefer to say the are equal, both 14 miles away, but the LGB drive is much easier, as it is basically leave the airport headed east to Disneyland (Ball/Wardlow). While John Wayne covers 3 freeways, heavy traffic, carpool lane options that can be confusing, etc.
I love the fact that both Long Beach and John Wayne have easy parking, and the fact the Rental Car Companies (well, at least the majority of them) have offices and pick up lots right next to the terminal.
And Long Beach just had a major remodel/improvement project. The new TSA security check in is awesome, a specific building built for TSA, and not add-on areas found in most airports. It makes the system work much smoother, as the set up was tailor made for them.
Some folks don't like the fact Long Beach doesn't have jet ways, and you board using outdoor stairs/ramps, but I actually like the old school method, and it isn't like there is much of a weather issue here.
So they are both great choices, and for many Long Beach isn't an option due to the limited flights and destinations, but for those lucky enough to have good connections from their home airport to Long Beach, it is my preferred airport in Southern California.
My list of all commercial airports in Southern California would be, with the most preferred at the top...
1. Carlsbad
2. Palm Springs
3. Long Beach.
4. Ontario
5. Bob Hope (Burbank)
6. Santa Barbara
6. John Wayne (Santa Ana)
7. San Diego Lindbergh Field
8. Tijuana (using the special crossover bridge from the USA in Otay Mesa with its special customs area)
9. LAX
That said, that is just the airport and has no bearing of where you are coming/going from.
But I would use the AMTRAK Pacific Surfliner to get from San Diego to the Southland (The Greater Los Angeles area including Anaheim), also for the trip to Santa Barbara.
To get to Palm Springs, while there are flights from LAX to PSP, they are few and expensive, so I would opt to drive.
Same issue with Carlsbad (Northern San Diego County), very few flights and expensive if taking just the one leg. so drive or the train to Oceanside and then a taxi.
But for those planning a large trip, sometimes picking Palm Springs, Santa Barbara or Carlsbad doesn't add much in price as compared to the big 5 airports in the Southland.