If you're a handloader, take a look at the 6.5x280AI. I'm considering building a lightweight custom rifle in that caliber. The 6.5x284 Norma is a great caliber also, if you wanted to stay on the upper end of the 6.5 range with factory ammo available.
Someone earlier mentioned that these rifles are carries d more than shot and that brings up an important point. If you ENJOY shooting your rifle you'll shoot it a lot more. I guide for my living in Texas and I have SO many guys with lightweight rifles in bigger caliber's that clearly don't shoot much more than to check their zero. These guys often fall apart when they have a trophy in the crosshairs. I'd rather have a hunter with a light recoil rifle, like a 6.5CM or .260 that enjoys their rifle and, therefore, goes to the range regularly and runs a couple boxes of ammo through it. Precision is everything. If you're capable of putting the bullet where it needs to go, the difference between 6.5 and .280 is meaningless. Plus, the lighter recoil makes follow up shots, if necessary, easier.
6.5CM factory ammo is exploding and there's many more options out there, with plenty of (expanding) availability. There's a lot to be said for a caliber where you can go into almost any gun store and buy ammo. Lapua just announced that they will be making brass for the 6.5CM - availability in Q1 2017. That's going to be another game changer for those that reload.
Aside from brown bear, I would have no qualms about shooting anything in Alaska with one of my 6.5s.
OP: if those 2 caliber's are the only options you have in the rifle you like, I'd get the 6.5 Creedmoor. You already have a .284 that, I'm assuming, you like. Getting another would be redundant; and, like I said earlier, recoil can become an issue when you're talking about light rifles.
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