There has been much debate on this point. Fingers have been pointed at the more developed financing infrastructure available in N. Cal as a key factor fostering startups. And there is certainly truth to this. Despite the recent explosion in incubators and accelerators in Los Angeles the follow-on financing is immature. This is important, but is it the most important factor? IMHO - that depends on what kind of company you are because that determines the kind of people you need and the bottom line is that the ‘staff resource pool’ of these two regions is very different.
The conventional wisdom is that N.Cal is stronger at hard core engineering and S.Cal’s strengths are in content/media. I am enough of a contrarian to not want to take this for granted so I have spent countless ideas browsing resumes. I wasn’t trying to prove S.Cal was as strong, as N. Cal on platforms, that was obviously wrong, I just wanted to truly know if despite the pool’s undoubted relative weakness it was nonetheless deep enough in absolute terms. I can now conclude that the conventional wisdom is dead on and there is real staffing risk ‘down south’ if you need to scale hard core engineering. Whilst it is possible to find such engineers there are !0x as many up north. Conversely if you want people with content skills there is no shortage in Los Angeles.
You may well be thinking that I have painfully arrived at the blindingly obvious. And you are right. There is however a wrinkle. It is not always obvious what kind of company you really are. Are you an engineering company or are you a media/content/entertainment company? In the old days this was perhaps easier. If I am building chips I am engineering. If making movies I am entertainment. But with media moving online this is trickier than ever. IMHO there are plenty of companies who may seem like content companies but whose core competence is in fact engineering. This is not to say that content is unimportant to them, but the truly hard problems they will face are engineering problems as they scale and if they don’t truly ‘get’ this they are destined to run into major problems. Technology is changing so fast that without reasonably ready access to the best possible engineers your platform can suddenly become obsolete and in this case the best content in the world isn’t going to save you.
Paul Graham wrote a fascinating piece on this very point which is worth rereading regularly. “What happened to Yahoo?” Of particular interest is his thoughts on the internal culture of Yahoo and how it progressively devalued engineering.
http://ils.unc.edu/annotation/publication/Fu_etal_ASIST05.pdf
You do not have to agree with his analysis of the Yahoo experience but the point is well made - it is not always blindingly obvious (especially to senior management who do not themselves necessarily have a tech background!) quite what your core competence is. Is Youtube an engineering company or a media company? What do their senior management think? One thing is blindingly obvious - the technical challenges of operating Youtube at its scale are enormous and ready access to world class engineers is mission critical.
You have to be somewhere that supports your core competence and for engineering that is N.Cal. The more technically demanding your platform/application the truer this is. The fact that there is less follow-on financing in S.Cal is nothing like so big a problem and N.Cal investors know it. Conversely, if you need people who truly grok content and the platform is likely to be reasonably stable S.Cal is the biz and if by leveraging this skill pool you build a great product IMHO you will find investors.
People are more important than money. Without the right people money is worthless.