I can't speak for the entire line, but . . .
We bought a certified reconditioned model 5200 about 5 years ago and it has been a real trooper. My wife makes juice drinks in it several times a week. I puree home-cooked pumpkin in it to make pie. It handles everything we throw at it. Just my opinion, but we feel no need for an upscale model. The variable speeds are nice to have. I can't express an opinion as to whether we would find 3 fixed speeds to be enough. I see that the TurboBlend Three Speed has the same motor as the 5200.
I hope this helps.
Joel