I didnt read the last couple pages of posts, but I wanted to make one point regarding LA vs. NYC.
Regardless of the fact that NYC is older thus has more diversity of old & new architecture, LA still can't compete, because it just doesn't have the GEOGRAPHY!
West to east, it roughly goes like this: Ocean | Basin (where LA is centered) | mountains
-and where LA (the city) is, its all flat, there are no rivers running through it, its one landmass, Everything's just plopped there. Now I know that it sprawls into the hills and whatnot, but the core of the city sits in a flat basin.
NYC on the other hand was built on a natural harbor. It sits on three major islands (not including all the little ones like where the statue of liberty & ellis island are). Rivers & estuaries run through it. Some parts are flat, some are very mountainous. I think this natural setting gives NYC the advantage in terms of architecture. The bridges alone take the cake! Find me a city in the country that has bridges as majestic as NYC's!
-Some more subtle things are places like Riverdale (going up to Yonkers) where its extremely hilly, and rock cliffs jut out. GIANT buildings are built on those cliffs, and tiny roads wind thru them, giving the passer-by a very interesting view. Maybe that's not specifically "architecture", but I think the landscaping of the city has some architectural flavors to it.