Well, I too am a lover of Santa Monica, having lived there for eight years back before it became Beverly Hills at the Shore. It still is beautiful, however, and would be a quieter place to rest your head. Lots of good hotel choices there.
That said, the Westin is fine as is the Marriott, just like the Westins and Marriotts are pretty much everywhere else. Both have airport shuttles, are within sight of the runways (is that really what you want??).
Just think: the Santa Monica beach is a 20-minute cab ride from LAX.
Have a fun time in Hawaii. Where do you stay there?
Regards,
Chuck-