Re: 375HH mag or 375 ultramag?
Well, here is my two cents. I've read the other guy's posts and it is all a matter of personal preference. However, here is my experience in Alaska over the last 6 years using the following:
.375 Rem. UltraMag w/ a Zeiss 3.5x10x44.
Two black bears and a 60" Bull Moose taken using the 300grain Swift A Frame. It packs a mean wallop out to long range. I killed my Moose with two shots at 501 yards according to the laser range finder. Both shots were through the shoulder only 5 inches apart and exited the ribs on the other side. Before anyone lambasts me for taking these shots, I practiced on the range for a year and burned through over 30 boxes of ammo with this gun. I tore up two sets of rings and a scope before getting every thing right. My comfort zone was easily out to 350, and I knew the ballistic tables from 0 to 600. The drop for my shot on the moose was 46 inches and both shots were true. Dead moose on the first shot, and the second was for insurance.
Kodiak Island in 2007 shooting 260gr Nosler Accubond at 2900fps. One nice blacktail, and was confident in the weapon when a brown bear stood on his hind legs to get a better look at me. Not to say the hair didn't stand up on the back of my neck. Thankfully, he decided to find a better morsel.
The Rem. Ultra Mag is one of the heavier commercial guns out there in that caliber. If you want to pay thousands of dollars, you can get a heavier safari-grade gun. Mine is 9.5lbs. unloaded and the felt recoil is more of a push than a kick, but it is substantial. I've shot the H&H and it has a fine reputation and is a great gun. I love my RUM, and it is equivalent to a heavier caliber gun when you look at down range energy.
You mentioned ballistics, and the best website I have used is JBM ballistics. You can look at trajectories, etc. for a wide range of conditions.
Finally, the .338 Win Mag. is awesome and cheaper to shoot than the RUM. It will take down everything Alaska has to offer. However, if you ever plan to hunt the Big Five in Africa, you'll need to buy another gun. Darn, I hate that (Sarcasm).
Good Luck and Good Hunting!