BlendTec and Vitamix are the same thing or at least in the same category and are probably comparable in price.
If you go with a Vitamix, don't throw away your blender because they each have their own uses.
Vitamix is more for completely pureying your food to liquid. A blender will still leave chunks of stuff and won't get it to a complete liquid. So all in all they have differnet uses. If you don't care about getting your smoothy or other things to completely liquid form, then don't buy a vitamix. If you do then get one. I have a Vitamix and a blender. For things like ice cream smoothies (oreo + vanilla ice cream + milk) I use the blender because I still like chunks of oreo and chunks of vanilla in the smoothie.
For things like strawberry smoothie (strawberries + ice) I use the vitamix because it turns it in to a true strawberry drink with no chunks of strawberry and no chunks of ice.
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