Yeah, I'm gonna go with the bear for this one. It's like kraco said, tigers and other cats are like animal martial artists. They do things like go for the leg muscles, tendons and ligaments to stop you from moving, and then move in for the efficient kill. While a grizzly can weight up to 1500 lbs, and a tiger up to 650 lbs (both approximate weights), you've got to look at your fighting chances here. The tiger's more agile than the bear. I could totally see myself outmaneuvering a bear, but a tiger? Nuh uh. So, give me an 8 inch knife and a 1200 lbs grizzly, and I think I'd have a fighting chance at killing it, or getting away. Against a tiger...nuh uh.
On the hot chick vs. kid half my age thing, I'd rather go with the kid half my age. The older I get, the more sense it makes. I hate losing fights when my opponent and I are pretty much evenly matched.