Re: 270 WSM or 7mm rem mag
First, I will admit that I am not a belted case fan.
I have seen several elk killed with a standard 270 Win, and even a few with a 2506 or 243. These were the rocky mountain variety and ranges were under 400 yards.
Were I to chose one of these it would be the 270 WSM. But I also agree with the statement about a bigger bullet selection for the 284. I would seriously consider the 7mm WSM. Were I to go bigger I think I would go with a 7mm Dakota, although brass is not cheap.
To beat a dead horse, bullet placement is key. If you shoot a hind leg off with a 338 or a 243, the result will be the same. Also, if you are recoil concious, like I am, and many people are and will not admit, then a smaller rifle that you can shoot well is better than a cannon that makes you flinch. Just my thoughts. Honostly, this class of calibers (WSM and especially the Dakota) is about all I want to shoot in a sporter weight rifle without some sort of brake.
Just one more opinion for ya.