RE: 7 mag vs. 7 ultra mag
I would go with a proven and more common 7mm Rem Mag. I personally don't see a need for the SAUM and WSSM rounds, why reinvent the wheel. It remains to be seen whether or not these new calibers will ever catch on. I personally wouldn't buy a rifle chambered for them. Shot placement is the key and familiarity with your rifle and how it shoots are the most important things.