When I was big into backpacking and climbing in the 70s everyone you met on the trail was your friend. You shared stories, food, drink, and sometimes when they were in need, clothes, medical supplies, and even shelter. Unfortunately, things have really changed since then. You can still be friendly, but you have to be on your guard at all times. The two legged critters are your biggest danger. For that either your .357 or your .40 will do. However, if your backpacking trip ever became a prolonged survival situation, the versatility of the .357 would really shine. A few rounds of .38 special for small game. I would hate to have to eat a marmmot, but if you got hungry enough . . . you could tell everyone else it was a short eared rabbit. I've heard that rattlesnake is good eatin'. The .357 loads for protection. Mountain lions aren't the toughest cats out there, and a .357 is enough gun for them. Here in Tennessee black bears have been harvested for years with them. (However, it's always better to be the hunter than the hunted!)
So between your two choices, I'd go with the .357.