I'd rather a 9mm,not for the bear but for the guide.
I can't out run crap, so putting one in the guides leg would probably give me all the advantage I need. :-}

I was once working under water putting up a tide measuring pole, it involved banging star pickets under water.
One of the guys I worked with knew I had a thing about sharks and said be careful as banging under water like that attracts sharks.
I told him that's why I had a pointed knife unlike the pry bar tipped knives everyone else was using.
He laughed and said you think that will save you from a shark?
I told him no, but if I stabbed him in the leg the shark would soon forget all about me.
He stopped laughing after that.