https://lao.ca.gov/laoecontax/article/detail/265
"Although California has had net out-migration among most demographic groups, it has gained among those with higher incomes ($110,000 per year or more) and higher levels of education (graduate degrees)."
Also, the age bracket for in-migration is 25-35. So the typical story of people maximizing their career potential despite high taxes. If they had the same career/income opportunity in a lower tax state, would they take it?
So, I don't think that the reasons to move from NY to CA have much to do with taxes. Having lived in both NYC and Norcal (on the peninsula), I can say that the cost of living in both places is in the same order of magnitude. For me, the main differences are that CA has much better weather and access to the great outdoors, but NYC has a more interesting culture and better food and commuting. I think CA is probably a better place to start your career as a software engineer, but once you're established, there are plenty of opportunities in both places.