The 7mm or 300 mag will need to have a brake installed to shoot comfortably for any extended period of time. As far as caliber goes it all really depends on what bullet weight you intend to shoot. Both cartridges are maximized when shooting the heaviest weight bullet possible for the caliber to provide the least amount of wind drift possible at long range. The 168-180gr bullets in the 7mm can provide the same wind drift numbers as a 190-200gr .30 cal bullet, but the 7mm can't match the .30 when its shooting the heavy 215-230gr bullets. The trade off is the 7mm uses a bit less powder and doesn't generate as much recoil as the .30 with the heavies.