I would go for the merrick before the nutro. The merrick has veggies and fruit in it. My dog didn't like the nutro as much and gave her pretty bad gas.
My puppy got HORRIBLE gas from the nutro wet food. I stopped giving it to her and gave her some better quality (eagle pack, canidae, innova) and it has stopped completely
When I was a kid we had a smallish ( 20 pound) mix dog and he got into a whole bag of hershey kisses. I thought he would have at least got sick, but nothing happened. Poop and everything was normal.
Still wouldn't want to chance it again though