The most expensive food is certainly in SF. Where the best is depends on the cuisine. What do you want to eat? If you’re coming from LA, maybe you don’t care about Chinese or Japanese, which is where San Mateo might beat SF.
I suggested CalTrain only because it beats the rush hour crawl heading into / through SF. Other times Lyft would be more convenient. In SF, CalTrain stops only in Dogpatch and SOMA (a short walk to Saison or Cockscomb), but at Millbrae it connects with BART, which can take you within a short walk of Benu and many other places.