Originally Posted by wilkup:
.45 ACP +P Ammo - 255 gr. Hard Cast FN (925 fps/M.E. 484 ft. lbs.)
Heavy 10mm Ammo - 220 gr. Hard Cast - FN (1,200 fps/ME 703 ft. lbs.)
Since the rounds that you are looking at function by providing deep penetration, the issue of choosing the one that suits your needs the best (bear? big cats?) is easily answered by using a bullet penetration model to determine how much penetration they'll offer against soft tissue. (Obviously, if heavy bone is hit, the situation changes)
For example, using the Schwartz bullet penetration model, the .45 ACP 255 gr HCFN @ 925 fps would penetrate to a depth of 30.98" whereas the 10mm 220 gr HCFN @ 1,200 fps would penetrate to a depth of 40.97".
Which one appeals to you more?