.270. All day long. Yes, I shoot one. And no, there's nothing wrong with the other calibres, but I have no experience of them. The beauty of the .270 to me, lies in its potential to be tailored to your exact requirements, especially if you handload. You have limited choice of bullets, which to my mind is a huge advantage as you're far less likely to the yourself up in knots. I use the 130 grain softpoint for all my shooting, with a relatively gentle load of 54 grains of h4831, and it's good enough to cleanly kill roe out to 300 yards. I don't shoot reds at great ranges, but it will still drop them on the spot at 200-plus.
It's an absolute beauty of a calibre, that's stood the test of time across the globe. I've not yet experimented with copper, but suspect 110 grain will be the way to go when I finally get around to it