I did an internet search "ipad case weight distribution" and this was the first entry,
a review of the 3rd gen. iPad Smart Case. Here is an excerpt:
Pop your iPad into the bottom of the Smart Case, and flexible rubberized edges form a secure fit while exposing most of the iPad's front glass. The case adds extra bezel around the edges, makes the iPad seem wider and a bit larger than before. Hand-held typing in portrait mode feels a tiny bit awkward, but for reading and for viewing media, especially one-handed (I ride a subway to work), it offers a comfy grip. Maybe it's the way the case handles weight distribution, but the iPad feels lighter to hold when in the Smart Case than when using a Smart Cover and a third-party back shell. It feels comfortable with the cover folded back, too.