its prolly cos the mxr use micro components, rather than regular sized resistors and caps etc. like most pedals. Ive spend some time with a blues pro and they are nice too, but yeah if you like the mxr, you can get the same sound from a fulldrive (i secretly think the MXR is a copy) using the boost and the mosfet mode, but it also has all the regular ts type sounds. Essentially it does everything all my other ts type pedals do, plus more. Its pretty well the only pedal i use. If im not playing straight pure clean jazz, then i just leave the thing on and use my guitar knobs, then on the odd occasion if i need more sustain then i step on the boost. It works well.
I do have some others and am always on the lookout for something even better, but yeah they are well worth it if you get the current one with the mosfet option.