My vote goes to the .270. There is so little difference in the two rounds that I find the extra recoil and blast of the 7mm magnum to be an unnecessary burden.
I have chronographed other shooters' 7mm mag's at the range for inforamtion purposes to see how they really perform, and in a disappointing number of instances the 7mm mag is no better than the .270, espeically with factory ammo.
The real hotrock 7mm mag's are those that are handloaded by savy shooters with access to chronographs. Individual 7mm's can ben goosed up substantially, but, in my observation, it takes a knowlegedable handloader with the time, expertise and willingness to embark on load development. You can get 3,300 fps with the 140 grain bullets and 3,200 fps with 150 grain bullets and 3,100 fps with 160 grain bullets. That is a material improvement over the .270, but some of the standard factory rounds that produce 2950 with the 150 grain bullet and 3,000 fps with the 140 grain bullet are simply not in any way superior to a properly loaded .270.