The .270 has put a lot of elk in freezers over the years. It's very close to the .30-06 in performance, and the only thing the .300s have over either the .30-06 or .270 is the potential for slightly longer shots.

However, my experience has proven to me time and again that even though slightly-built deer and pronghorns can often be dropped at greater distances than one might imagine, elk are tough and demanding of marksmanship rather than unreliable expectations of ballistic "power." Buying a bigger caliber isn't a sure cure to be able to take pokes at elk on the next ridge over. Any hunter who lulls himself into thinking so is probably going to be in for a lot of trailing and lost elk.

If you're thinking that you want to be able to lob bullets across to the next ridgeline, you need to be thinking something more in the class of the .338 Lapua. I've yet to see one of those that I'd like to lug around in the high country, though. Something about those "long tom" barrels...