I wanted a Dianese but they didn't have it in my size. They are probably considered to be the best.
I ended up getting a Teknic, it was around $75 bucks, very comfortable, and was about $150 bucks less than the Dianese. I had two low sides at the track at over 100 and walked away without a problem. On the second wreck my head snapped back pretty hard so the right side of my back muscles were sore, but the back protector did it's job.
I honestly think that Eyespy should really answer the question, "Is any backprotector a backprotector". Since he's a doctor he probably knows better than anyone here. :thumbup