Two good quality resins used within the windscreen replacement Industry, each with their own unique features.
Esprit - The market leader by far and one of the worlds leading brands sold in many countries in Europe and the Rest of the World. Meets BS AU 251:1994 and BS AU 242A:1998 which are related to Specification for performance of automotive laminated windscreen repair sytems. Esprit only sell their own resin and DO NOT supply any other company with their own brand resin (including REJEL) Esprit resin is distinct in that it has a slight straw colour and comes in a white bottle with a black lid.
REJEL resin - Rejel's own brand resin is a top quality resin, being produced in America and used by other leading windscreen repair companies. Also meets BS AU 251:1994. Rejel resin is clear and comes in a white bottle with a white lid.
If you go to Sainsbury's you have a choice of Kellog's cornflakes or Sainsbury's own brand. Both are suitable as a breakfast cereal and give excellent nutrition but people have a preference. Some like Kellog's because it is a long established brand and they feel the quality is better. Some prefer Sainsbury's because it offers better value for money, meets your nutritional needs and still fills you up at breakfast time.
But to sum up, both perform an excellent job giving good results. It is just that people make their own choices with which resin they want to use!!
I prefer to drive my Lexus rather than a Mercedes or BMW but I am sure you have all got your own views on that.