Moving to SF from LA, I have experienced a massive Yelp inflation. For example, Burma Superstar is very much not a 5-star place. I think a LA equivalent rating is more like 3.5 for Burma Superstar.
Using a standardized place of reference, such as Starbucks, which is equally bad/good/mediocre across locations, here is a simple way to calculate Yelp Star Exchange Rates.
Requires a JSON file with Yelp developer credentials
Using
get_ratings_in_city('starbucks','San Francisco',hoods_df)
the mean StarBucks rating in LA is 3.36 compared to 3.41 in SF. Not a huge deal but a deal.