I do have a blendtec I bought from Costco on this same deal few months back. It is awesome, but sometimes I wonder if it really has a practical advantage over Ninja which is around $200 cheaper if all you are doing is crushed ice smoothies etc.
We borrowed a Vitamix for a few weeks to try it out. Then we bought a Ninja. Even for things like smoothies there is quite a bit of difference between the two. In our case the difference wasn't worth an extra $200+ but I definitely wouldn't fault anyone who went Vitamix/Blendtec over the Ninja. The Ninja is a pain to clean vs the Vitamix. Something to consider if you use it daily. Over time that convenience is pretty huge.
All in all - if you have the money and plan on using your blender frequently go with Vitamix/Blendtec. If you use your blender a couple times a week at most and want to save the money stick with your Ninja.