Is it better living in London or Los Angeles when it comes to the quality of life/surroundings/quality of people?

This is next to impossible to answer. There are SO many variables.

Year 1987 Los Angeles. London was sugffering from East End losers and The suffocating English Middle Class and their fake smiling dominance.

Year 2021. London. London now owns Los Angeles in everything apart from weather. It is an amazing City while L.A has self imploded.

Most people don't have a choice, unless you have dual citizenship you won't get a work visa especially for a sector that is already well-subscribed.

London is better than Los Angeles but California is better than England. 

Unless you have British and American citizenship you don't have that choice, so 'better' is irrelevant and no you would not get a work visa to do an admin job

As for the first question, that all depends on what life, surroundings, and quality of people you prefer. The two are very different. Apples and oranges. As for the second, 'administrative sector'? That's not actually a thing. If you're talking about jobs in government, know that you must be a British citizen to work for the British government.