Either of the bullets in the calibers you mentioned will work. Black bears aren't all that hard to kill, but you do want something that will penetrate through and through while still giving good expansion. Nosler Partions are a great choice and I will be using them on my bear hunt next week. I hope you have a great hunt.
I'm hunting Saskatchewan black bear May '08 - use your BOW
Everyone I've talked to says that black bear (over bait) is a definite bow hunt. Provided, of course, that one is proficient with a bow (min. 160 lb. draw / 125 grain non-mechanical broadhead).
From what I've researched, many good options on rifle for black bears - 30-06, 7 mm magnum, 300 mag or 300 WSM plenty powerful - should be at least a 180 grain - nosler partition a good choice. I like the Accubond round personally - took down a 1,200 lb. moose in 2004 with one well-placed shot.
As the allure of hunting big whitetails becomes more and more a passion for many, we are finding that the recent (historically speaking) popularity of hunting deer from a tree stand is becoming the way to do it. I'll make no statement either for or against that technique here. This will be simply an essay on what I feel are some outstanding rifles for tree stand use.
Before we go even one more step, let's all remember that safety is first and foremost for anyone wanting to hunt...