As a new owner of the Ninja BL800 Ultima Blender, I can definitely say that this model does make wonderful fruit-smoothies. The 3 exceptionally-sharp blade-sets do a very good job of pureeing fresh and frozen fruits and vegetables. I hope that this helps.
I've never used the Nutri Bullet, so I can't really say if they make the smoothies the same, but I make smoothies several times a week, using fruit, frozen and fresh, protein powder, yogurt, ice, nut butters, almonds--all sorts of things, and they all come out smooth, whether thick or thin. Much better than anything I've used to make them before.
Yes, it is really powerful, much more powerful that Nutri Bullet.