Commercial property -- to which I'm including multi-family residential for this post -- is almost definitely the bigger problem. The reason arises from the fact that these properties very rarely trigger a reassessment of property taxes and as a result tons of commercial property owners are paying 1980s era property taxes. Firstly, commercial properties are often held by long time/indefinite property owners -- companies -- who rarely sell and don't "die" (deaths especially those involving split inheritances commonly cause property sales which trigger a reassessment). Secondly, in the event a company does sell, they can usually avoid triggering a reassessment by only selling a "stake" in the property. If that stake is below a certain threshold, there's no reassessment. You can read about this by googling "close the prop 13 loophole". Residential properties are very simply reassessed more frequently on average than commercial and this problem is going to get worse over time.
Oftentimes, properties in California (especially multi-family residential) are owned by a corp/LLC which owns nothing other than that single property. That corp is then owned by a larger company who can sell a stake in single property company if the right buyer comes around. The CPAs have avoiding a prop 13 reassessment down to a science. If you write a rent check to a company that has your street number or street name in the company name, that's why.
Much of valuable property in this state was developed before 1978 and as a result the owners are paying just a fraction of what their taxes would be after a assessment. Sales and income taxes are subsidizing this difference. Now, the counterpoint to this is that raising property taxes will result in some of those taxes being passed on to renters. While this is true, not all of it could be due to simple supply and demand. The worst offenders will be able to pass on the least of that difference. The state would also be able to lower corporate, sales or income taxes as a result of phasing in market property taxes too. Maybe that last part is just wishful thinking on my part.
Regardless of your take on residential vs commercial property and prop 13, this is a problem that is only going to get worse with time. With no changes, 50 years from now, there will literally be people and companies paying property taxes like it is 1990. The result is that in order to make up that difference, corporate, sales, income and "new" property taxes will have to be higher than they are today. If those other taxes rise enough, people leave the state for greener pastures and property values fall or stagnate which is another more painful way to equilibrium.
Significantly higher property/land taxes in this state than we have now would solve or curb a lot of problems. From housing bubbles (probably merely curbed) to encouraging cities like SF to build more densely to allowing lower income/sales/corp taxes to encourage investment, many of the states problems were created or exacerbated by prop 13. When Warren Buffett was Schwarzenegger's economic advisor during the campaign he said that prop 13 doesn't make sense. He was right.