I've done recent contract work in both SV and LA. I would say SV/SF pays 10-15% higher. In addition the work in SV is much more interesting to me and probably other HN types than the work in LA. Within the Bay Area the arc from Berkeley, SF, Palo Alto, San Jose was more interesting than the East Bay/Contra Costa.
I used CraigsList so there may be a SV vs LA bias in the listings.