A question for hobbyists.  What percentage of ads that you check on EROS or Exotics pan out when you find reliable review information on the providers?

The key words that you stated were "when you find reliable review information" will partially answer your own question. If you find a well reviewed lady with a decent reputation then I would tend to trust that ad pictures are indeed accurate, rates and service will be provided as advertised without any hassles.
I think it depends on which city/region you are in, to determine the percentage of overall ads that may or may not be completely true, accurate, and up to date. You seem to be on the right track though, always do your homework and research those reviews to find out the legitimacy of any ad.
In my particular region, Eros used much more than others, we all tend to know the local ladies' reputation (good or bad); it's the traveling ladies that we must research (once again good or bad).      Of those that have been well reviewed by a couple of respected local  hobbyists, very high percentage (like 90%). Otherwise, it's anybody's guess.