I'm checking back in here, following my posts above. I did go to San Diego, but also made the most of an unforeseen opportunity and did LA too.
My expectations for LA weren't particularly high, however I did enjoy it. Yes, it had its challenges, especially photography into the round house cages, but other things made up for it.
San Diego; far more compact than I expected and although it blew me away quality wise it wasn't perfect - again their chosen mesh and glass made photography impossible at times, for some exhibits.
San Diego wins, but it was a closer contest than I expected.
I posted some LA photos in the gallery, San Diego will follow once I get chance to process many many shots. Pangolin pics posted for now.
Thanks very much to the posters above for the tips, you made my trip.
cheers
Nige.