You can't go wrong with either the 7 mag or a .280 Remington, but the short mags have a built in disadvantage you may not have considered. If you intend to combine long for caliber bullets, particularly the mono-metal TSXs or TTSXs, with case filling slow burning powder, the short body and neck of this cartridge can result in the bullet robbing powder space if seated deep enough to cycle through a short action magazine. Suddenly your Wissm has the ballistic potential of a 7X57, not that there's anything wrong with a 7X57, but its not a 7 mag either.
If minimizing the weight of your hunting rifle matters to you, it should be done through the choice of proper stock material, barrel length and contour, and not through the choice of short action over long unless you wish to use a 7-08, which seems to minimize the disadvantages of the over bore short mags.