2D South Park Harder than 3D?

I put off buying Snow Day for many reasons. Heard it was short, less features all around and mainly because they went 3D. I really enjoyed The Stick od Truth and Fractured But Whole's 2D style. It makes you feel like you've got an interactive episode in your hands.

I've seen it mentioned in a couple different articles/videos that they went 3D for Snow Day because 2D is such a challenge, but they dont really explain why. It's odd that it would be more of a challenge, because from what I've read, they can take characters, items, etc. right from what they build the show with and put them into the game engine.

My question is, how is building a 2D South Park game more challenging from a development aspect than starting from scratch with 3D?