There are several different neighborhoods even in Santa Monica. I live in Sunset Park which many call one of the last Ozzie and Harriet neighborhoods in LA. It is often has a small town feel but on the westside of LA - with easy access to all LA offers and the beach. Moved out here 17 years ago from the east coast and would not want to live anywhere else. There are also many new apartments/condos opening so PM sent to OP - happy to answer questions.

That said there are many great areas in LA. An older colleague who came back from an expat assignment in London and got used to city life there and not having a car ended up selling their house and moving to a condo in Long Beach when they came back - they really loved the downtown LB lifestyle. And Pasadena reminds me a lot of Bethesda, MD where I moved from. I would probably live there or Glendale if my work was on that side of town.

I think anyone moving out here should do something short term, experience the everyday for a while, and find their center - then pick where they want to be based. LA is really more a bunch of neighborhoods strung together than a single city (even though we now have a more useful downtown). But also seems like the OP is familiar with a few areas - and I cannot argue with Santa Monica being a great choice!

if you look at Flightaware the inbound routes from the Pacific and Asia already come overhead. I live by the Santa Monica airport and my kids love planes - we are looking at them all the time and can usually identify with the naked eye (the LAX bound planes). Unless they were to reorient the runways at LAX so there was a direct southern landing approach, not sure Santa Monica airport closing is going to change the LAX approach for Asia/north all that much. They will most likely still come over Santa Monica on their way to downtown before turning back to LAX. Maybe a little lower - but I doubt it - they are still flying over the entire westside of LA's population.