RE: 7mm Rem Mag vs 30-06
I've shot deer with both. As far as terminal performance goes, there is no difference between the two.
I prefer the 30-06 b/c ammo is much, much cheaper (about $8-10/box in my area).
Also, with regards to trajectory. If you are good enough to be shooting at an animal at 400 Yds, you should be able to compensate for the difference in trajectory between the two at this distance, which is only a few inches.