I disagree. What's the biggest bullet you can load in the .270 WSM, 150 grains? Maybe 160? I'd rather shoot a bull elk or moose with a 180 or 200 grain bullet from an -06 than a 150 or 160 grainer from a .270 WSM. KE be damned! I want a bigger hole and assured penetration!
I have shot moose with a 150gr 308win, 200gr a-frame 300RUM, and 180gr 30-06. All fell down and went boom. I have witnessed moose taken down with a 270 150gr. And that same day a woodland caribou. All fell down and went boom.
One thing I learned in Newfoundland, its not so important the gun or the grain, as how good shape you are in. Better shape more land you can cover.
A trip to northern Newfoundland, I worked and worked all year finding the perfect load. I fell down off a hill on my scope and knocked my scope out bad. Well, I borrowed the cooks gun and took a cow next day. It was a 308win. That day I learned I should have put alot more effort into stair climbers and taking offhand shots.