I don't have a huge problem with a $10.10 minimum wage, because the market price for unskilled labor is such that this price floor wouldn't result in too much job loss. On the other hand, evidence like this shows a $15 minimum wage can be a real problem for the marginally employed. An effective or binding price floor on labor will result in an increase in unemployment, and $15 is just going too far.
Prices and wages tend to be higher in cities, as often are the requirements to live there. I have no problem with big expensive cities like LA experimenting with higher minimum wages than most other places.
OK, perhaps $12 or $13 would be better? But if we're at a point where unions want to negotiate lower wages, then we've overshot.