When I missed the postman with my opro gold, I picked up one of these as a last-minute substitute so I would at least have something for training. Having now used both I can say the difference is amazing. The bronze is hard and tough to bite into when heated, you have to mold it two or three times to get it to shape, and it just plain hurts. The gold molds easily and softly to your teeth on the first bite.
I understand the silver and gold models in the opro range are made of totally different materials to the bronze, so my advice would be even if you're after something cheap it's well worth spending the extra couple of pounds to upgrade to silver. You truly will not regret it.