These figures are from Wikipedia.
Grizzly bear, adult male, Alaska: 390kg
Grizzly bear, adult male, Canada: 140kg^[1]^
Bengal tiger, adult male, Chitwan: 260kg^[2]^
There's some variation in tiger size too, but much more in bear size, it seems. It could be a 2:1 ratio either way, so the question is if that size difference is enough to determine the outcome. Maybe we should compare fighting styles for these two animals.