My wife had a "smoothie" made by a co-worker that is based on green apples and raw red potatos.  Our smoothie maker can't do that and leaves unchopped bits and a gritty feel.  Her friend uses a Vitamix blender, and looking up the model number not only induced sticker shock, but reviews raised concerns with the item leaving bits of teflon in the food etc. And the price for just a replacement pitcher is so high that it appears overpriced.  What is it about a blender that allows it to make a good purée rather than just mixing things easily?  I think it might be the design of the blade and base, not just raw power: even a modest powered blender doesn't stall or run out of power; but it doesn't chop any finer no matter how long it is left running.  It might also involve speed vs torque usage of power.  Does anybody know what makes a machine capable of making a good purée as opposed to just blending, especially when both kinds are sold as “blenders”.  Should I be looking for ones with different options for blades like a food processor, to make it well suited to different purposes? E.g. I have seen blades just for milkshakes.  In general, how do you shop for one when the only information a seems to be total power and the number of presets? 
   In general, how do you shop for one when the only information a seems to be total power and the number of presets?   Product reviews from real users is your best tool. Problem: it is time consuming to read many reviews and weed it down to the helpful ones, and the comments are not always accurate.  I heavily rely on Amazon reviews, even if I don't end up purchasing there. What I like about Amazon reviews is the "ask a question"  feature. For example, you could ask "can this puree an apple, not leaving a gritty feel?". When I've asked questions on a popular product, I've gotten same day answers. 