I didn't want to skew the replies, but the reason for the question is a feller in Alaska says carries the Colt for bear encounters while logging. He says the 10ga will mushroom out and not penetrate to the vitals like the colt with hard cast will. The book energy comparison puts the favor firmly in the slugs court with 2785 ft/lbs vs the Colt's 1172 but pumpkin ball slugs are usually dead soft lead and I thought he may have a point. I just wanted to ask a bear hunter to see if they would agree.
Ian
10 ga slug, 766gr, 1280fps, 2785 ft/lb energy (Federal factory load)
45 colt, 325 hard cast, 1275fps, 1172 ft/lbs energy (Hottest load I could find on a quick search)