I have used the 375 H&H in the past and know several folks that use 45/70's. Both can produce excellent results, depending on your style of hunting. Of the two, I much prefer the 375, because of its versatility. The 45/70 in Alaska is kind of a specialized tool, short range - deep brush work. The 375 has more power than needed for anything other than the biggest of the coastal brown bears, though it will definitely work for anything. I would not want to lug a full sized and weight 375 into the sheep or goat mountains, nor would I want to take a short barreled lever action 45/70 into those same mountains. Both could do the job, but would unnecessarily place limitations on the hunter.
Most of the posts we've been seeing about Alaska focus on the biggest of the bears and that is such a small portion of what Alaska has to offer. They are magnificent animals and do command respect, but if you are wishing to come up for a moose and caribou hunt, I wouldn't worry about packing for bear and just bring a good 30/06 if you have one, or any other rifle with sufficient steam to penetrate and kill a moose 250+ yards.
Most 1 rifle hunters up here carry either a 30/06, 300 Mag, or 338 Mag. Any of these will handle any hunting requirement and do it very well. If in areas known for big bears, just load heavy premium bullets. While in the sheep mountains, lighter more aerodynamic bullets.
The problem with big guns are just that they are long and heavy or overly limit the range. A 10 or 11 lb 375 isn't a big deal if you are on a float hunt, but scrambling around in mountains for 10 or 12 miles it becomes overly burdensome.
