Last ditch for what? If you are in the woods a fear a bear attack and you must use a handgun, the 44 Mag is just fine(as fine as any handgun is going to be). If you mean the SHTF weapon(total break down of society a we know it), then some other handgun will be better. This scenario requires lots of ammo, which means light enough to carry. There is no sense in having so much ammo that all you can do is sit around and defend your pile. My choices would be:
1. A good 9mm semi auto, with lots of mags, ammo available and light.
2. If has to be a revolver a good one in .327 Magnum. Light ammo, reasonably light weapon, can be used effectively for survival or defense.
3. A good 38/357 Special revolver, ammo all over and reasonably light.
4. One of the Kel-Tec 22WMR semi autos, lots of 30 round mags, very light weight, can carry lots and lots of ammo, good for survival or defense.
5. If must be a revolver, 22WMR S&W 651, possibly a 22LR cylinder. Again, lots of ammo, and an effective weapon.
Anything larger than above brings in the problem of weight of ammo, availability of ammo, and other considerations.