where

Could you tell me where I can find an objective comparison of the terms and conditions offered by legal and offshore bookmakers?

There’s an excellent analysis at https://www.oddstrader.com/sportsbooks/offshore-versus-regulated/, where the author has laid out all the facts without any advertising. Official bookmakers offer full legal protection and transparency, whilst overseas services have the edge thanks to low margins, a wide range of markets, no betting limits and complete anonymity.