In a nutshell as of April 2011 Condo prices in San Francisco were only down 14.5% from the peak of the market in 2007 as opposed to Los Angeles' whose overall market has fallen 38.6% as of February 2011 from its peak in September 2006. Note though each neighborhood and community is different so it is better if you were to actually compare on a neighborhood by neighborhood basis as some neighborhoods have actually seen an appreciation in condo prices recently while others continue to decline.
To get a good idea for what is currently happening in San Francisco with regard to Condo and SFR (Single Family Residences) pricing go to our Marketing Reports page.
To see the article itself on Trulia about who has the best condo resale value San Francisco or Los Angeles click here.