I'd have to say it depends on your situation... My slug gun gives me a range out to about 150 yards. I'm not familiar with the S&W 500 rifle, but I'm sure it can reach out a bit more than that... Some farms I hunt I could potentially have a shot at 300 yards across the cornfield, so I'd take the rifle for the extended range. Other farms are thick woods and timber where an open shot is more like 50-60 yards, I'd take the slug gun for the 1 oz slug and bigger hole.
"When a hunter is in a tree stand with high moral values and with the proper hunting ethics and richer for the experience, that hunter is 20 feet closer to God." ~Fred Bear