Walk of the Dead 1 has eight different sculpts, with three of each. I think these are the same as in Season 1. WotD 2 has four sculpts only found in that box - if I remember correctly, the remaining four sculpts are duplicates from box 1, but I might remember wrong.
Edit: Found a picture of the box 2 contents. Seems to be eight sculpts, all of them different from box 1, and three of each. So if you get both, you'll have 16 x 3 zombies. That said, the VIP zombies are mucho cool.