Well, I personally was carrying a SP101 for woods duty, and I own a few .40's, but when it comes to woods I really feel that it's best to have something a bit bigger.
I'm not saying that a .357 or .40 wouldn't be fine in many woods oriented SD situations, but I don't want to risk it when it comes to the meaner beasts. I'd rather have the GP100 that you already have (although I understand why you don't want to lug that sucker around).
When it comes to boar and bear, I want the something a bit heftier than any of the common SD calibers. I thought about going with a .44, but I do some pretty tough backcountry hiking/camping and I just couldn't see myself hauling around a Redhawk or something of the like. I could have gone with a lightweight S&W in .44, but then I wouldn't want to get any decent practice (aka hand pummeling).
So I settled on a 10mm, a G20 to be exact. I think the 10mm is pretty much the best way to go for East Coast woods duty. The G20's a bit large, but it carries just fine in a fanny pack (and I'm already toting a 50lb backpack). Of course if one was turned off by the size of the G20, there's always the considerably smaller G29.
Anyhow, that's my take on it. You'll get a ton of input from the "nothing smaller than a .44 mag" crowd, but there are other options. Truth be told, the .357 isn't a meek caliber. If I had to choose between your choices I'd go with the SP101 (I have a serious soft spot for SP101's and carry one daily). They are truly amazing guns and many, including myself, believe that they are the best snubby out there.