The creation of objects, and the set up of the scene is exactly the same in both programs. The difference is the animation.
In the Invigorator you have to use AE's keyframes to animate the objects and camera. Oftentimes this can be frustrating and very time consuming, especially if you are doing anything fancy.
In the ProAnimator you create animations without using keyframes. There are controllers for animating the shape of the paths, where objects will start and end, and the timing of the objects as they move along their paths. By using controllers rather than keyframes it is much easer to create the animation and you can do it in far less time. Once an animation is created you can save it and apply it to any other set of letters or objects. This means you can create additional versions without having to recreate the animation.