My take on stuff like this may differ from some others. What I might choose to "hunt" bears with would likely be quite different from what I might choose to "defend" myself from a biting critter.
If I'm hunting, (that's an offensive action) I can use both hands. In a defensive situation I just may not have that luxury. For me, given that reality, I'd have to choose a DA revolver or a pistol in a decent caliber. I know what MY limitations are when shooting multiple shots quickly with only one hand, and with a SA revolver - it ain't pretty. And forget the possibility of having to shoot a SA revolver quickly with just my off-hand!
Once a big critter is on you, only a hit to the CNS is going to predictably end the thing quickly and under those circumstances you just need a round that will penetrate at contact distance.
I know some of you remember seeing the still photo sequence of a western state game warden being drug off the back of a pick-up by a grizzly he had just released from a relocation trap. He took a bite or two, but he fairly quickly killed the big sow with his duty sidearm, a .357 revolver.
I don't like either of your choices, but knowing MY limitations as just described, I guess it would be the little SP101 revolver loaded with some 180 gr Buffalo Bores. Even from an abbreviated barrel, at over 1200 fps they should penetrate adequately.