I would honestly be much more concerned with predators of the two legged variety. Much of this "which handgun is suitable for bear defense" is based in theory since bear attacks are such a rare occurance. Since such attacks are so exceedingly rare no matter the location, there are very few examples of defensively using handguns in such a manner or individuals with any actual experience.
I do think the distinction should be made that all bears are not the same...
"Unlike Grizzlies who attack out of territorial and dominance issues and are very difficult to dissuade, black bears see humans as a source of food: black bears can normally be dissuaded easily by hurting them-you don't need to kill them, so any reasonable powerful handgun cartridge, such as a good stiff 9mm load that penetrates deeply will discourage them and probably kill them anyway, if properly hit. Since many folks who frequent the woods already own a good 9mm or .38 special, they can choose proper ammo and be well armed." - Buffalo Boar founder Tim Sundles
"Black bears are generally not a huge issue and you could probably get away with most service calibers. Brown bears need something like a 12 ga w/a deep penetrating slug or a hot .45-70, not a handgun"... -Ballistics expert Dr.Gary Roberts(aka) DocGKR.
I would recommend arming yourself with whatever you feel comfortable with and go and enjoy yourself not being concerned with bear attacks all that much. In your situation, I myself would probably take a 9mm Glock. If I felt that somehow inadequate, I would take a 10mm Glock. In terms of revolver vs auto(642 vs SD9 in your case), I think the capacity advantage and usefulness at greater ranges of the 9mm semi-auto outweighs the potential need for a contact shot(s) where the revolver might be more effective.
Just my opinion, YMMV.