If you have a Redhawk you can pop in stout 45LC loads and "wake it up" for bears. For home defense normal factory 45LC loads are great (basically a duplicate of the .45ACP which is considered among THE finest man stoppers ever created!). I am not really one to recommend over loading 45s though. I think you are better served with a .454 Casull that you can drop 45LCs into for personal protection.

The 44mag is a great big game caliber but far from ideal for home use. The problem with it (or the heavy .45LC loads) are over penetration which could be of concern in the home as you could shoot through an attacker and wound a family member in another room (or if you live in an apartment/condo you could shoot an innocent person which would be DOUBLE LAWSUIT CITY!).

Of only the two you mentioned I would say go with a 4" barreled 44mag. The 4" will pack/conceal easier and is easier to handle quickly in the home as well. For home use I would advise you put .44Special rounds in it. Then it is a GREAT manstopper without as much worry for over penetration. When backpacking stoke it full of quality hunting grade hollowpoints.

Good luck,
RA