I'll tell you why 
The 3D models are rendered in very high quality. It has the same content for showing what moves the Pokemon learn and all. One thing that is MUCH better than the 3DS version is that with the older characters, the PokeDex data goes back to the original Red and Blue. I also think that once the 6th gen is released in October, The Pokemon Company can easily update this app with the new characters. For the 3DS one, we may have a whole new and separate program, just as how the original PokeDex 3D was released for free and had the Gen V characters, only to have another standalone PokeDex with all of the past characters.
I did get the 4th gen iPad last Thursday in preparation for my new job at a new daycare. I majored in Early Childhood Education, and I've worked with infants to school age children as a floater. I left my past center due to some problems, but I'm getting hired by a new daycare (I have to travel to it in another city which is 35 minutes away!), but this new center is more progressive as they want to integrate technology into the classrooms. So they are getting iPads as well.
For me, I got this iPad (64GB) for my specific educational purposes. I have a lot of National Geographic apps, a Sketchbook Pro drawing app, some outer space apps, the PokeDex iOS, Audubon (birds, butterflies, ocean animals, insects/arachnids, mammals, reptiles/amphibians, fungus, trees, and wildflowers). I also have some other things such as math and whatnot. I also have my therapeutic music on it, and that takes up more space than my apps.
Honestly, I've heard that there is the iPad 5 coming out later this year. I can care less about that, as the one I got serves me well for what I need. I will only change to a better iPad if mine breaks or gets outdated in 3-4 more years.






















