First of all, in the USA at least the slug load is an offering of one! The federal foster slug in 1 3/4 oz. It kills deer easily and works ok on bear as long as lung shots are used. It will fragment on shoulder shots on bears over 350 pounds.
I have used both the #4 buck and 00 buck loads on deer. They kill ok, based on distance and pattern in your gun. I would not use them on large bear. For deer, I shoot for the head with buckshot or a side lung shot.

I have played with the 10 many years and own an H&R 36 inch single, an Elibar bouble barrel that I bought sawed of at 20 inches and a Remington SP-10 with a 26 and 22 inch barrels and factory screw in chokes.