Whenever I go to LA, it seems like an urban slum with no significant development of note (above 6 story) in most of LA. Its as though the land is worthless, even Oceanside has taller buildings than Long Beach or Riverside, and Oceanside is literally the middle of nowhere California!
With that low density style of development, your not going to be able to justify a rail line that can move 20k people an hour, as there aren't enough people who can get to a station to feed it.
I blame LA's zoning that keeps it as an urban slum. Dezone the city and you'd see areas around existing mass transit densify over the next decade.
Its an hour from anywhere (about even time wise in my experience, whether heading to San Diego or Long Beach), has a beautiful coastline, but there is a gang war currently raging there and it is a rural small town, and that is how it operates (alongside the county gov't in North County).
Hell, there was a murder last week not a block from where I walked daily when I was there a few weeks ago. Had a window get smashed there too a few months back. IMO, Seattle is safer (just gotta keep the crack heads from breaking my windows in Chinatown :P).
I've yet to see any sort of metric (certainly not the US Census) that supports that claim.