I own both .44 Magnum and .45 Colt revolvers.
If you already have a .44 Magnum, I don't see the point in getting a .45 Long Colt.
You don't need a premium bullet. A simple semiwadcutter cast to wheelweight hardness will do the trick.
Frankly, the best close-up defense against black bear is a 16 or 12-gauge pump shotgun. It's what the Canucks carry around my cabin in British Columbia, where black and grizzly bear are common. Anglers fish streams with folding-stock Remington 870s and Mossbergs slung across their back.
The first load up is 00 buckshot, followed by slugs. The reasoning is that you'll be startled with the first shot, and need a little wider pattern to ensure a hit. Follow that up with Foster-type lead slugs (the classic slug).
The Canucks I've talked with aren't impressed with the Super Ultra Turbo ZX-500 slugs sold today. At close range, the classic Foster slug works as well, I'm told.
I keep my Browning A-5 semi-auto 12 gauge loaded at my cabin as above. I've never had a bear threat, so I've never shot one.
Keep things in perspective: If you have to shoot a bear, you'll be doing so at very close range. A bear at 75 yards distance is not yet an imminent threat. You'll almost certainly be shooting at 25 yards or less, so you don't need a super-duper bullet or slug to do the job, or minute of angle accuracy.