I don't have the Vitamix or the Ninja but it is my dream to have a Vitamix to make nut butters and ice-cream.
I have researched many blenders and none of them (Including Ninja and Blendtec) can compare to the powerhouse of Vitamix.
In the video above (And many others I have seen) you can clearly see how easy it is to make peanut butter with the Vitamix but with other blenders you have to keep opening the blender and mixing (Just like I do with my old-faithful Oyster blender).
Come on, if these blenders call themselves pro then they have to do the job of a pro blender like the Vitamix.
Of course, pricing is a killer but you can also get refurbished ones at a decent price.
Vitamix ALL the way.