I have only held the Stevens, but I bought the Rossi Tuffy Turkey.
My son is 8.5 years old, I like the fact you can remove the stock spacer in the Rossi. I didn't see any information about changing the LOP on the Stevens, but I don't think you can. With the stock spacer removed he can get on the gun properly/comfortably.
I really don't have a complaint about the Rossi. It doesn't seem like either would be a bad choice though.