As always, shoot the most you can handle because good hits trump bad misses. Some guys over gun themselves & the heavy recoil only gives them one shot. The guys shooting small calibers will probably get some hits on target but bullet selection is very, very important. Heavy, hard bullets are best.
Something that can cover 30 yds in 2 seconds can get your attention in a hurry. Almost forgot, how fast can you get your gun out???
The 9mm shooter was shooting from the side, he wasn't the one being attacked. Also he's one of the best bear guides in Alaska. Choose wisely..........

Dick