Depends on what you plan on blending. As another poster mentioned this will make smoothies, much thicker than juices and you may want to add water to help digestion.
I make kale shakes every day with cucumber, celery, ginger, kale, etc. The ninja makes more of a watery salad, while the vitamix I now own will puree anything I throw at it.
If you plan on using fruit mostly, the blenders you mentioned should be fine. If you want to do any thicker cruciferous veggies like kale broccoli or the like you might want to save for a vitamix or blentec. I personally like the vitamix because it came with a nice tapered plunger to push down the veggie stuffs.
Good luck on the new addition to your diet!