Welcome to the forum Jason. The most important question is to ask, in earnest, what you will use the rifle for. Are you shooting deer within 200-300 yards? Elk? Bear!? Obviously if you are trying to harvest tougher game then a heavier caliber is preferred. That being said, there have been plenty of elk and bear taken with a .308. Then there is range. Are you going to be shooting at bighorns in the Rockies from one side of a mountain to another? The higher BC, better energy retention of the 7mag will serve you well.
Next question will you be carrying this rifle? Is it a range toy and the furthest you carry it will be 100 feet to the firing line? Or 1/4 mile to a tree stand for deer hunting? Or are you trekking out in the Rockies to harvest a bighorn? If you NEED a light rifle, the lighter caliber begins to look more appealing. I've had a sub 8lb 7 mag rifle, and it was not fun to shoot. Also .308 has less of a velocity loss out of shorter barrels than 7mag, so it's easier to get to that lighter weight rifle and maintain velocity without a straight up pencil barrel.
Next is a question of barrel life. If you want to spend a good bit of time on the range with it, .308 is much more barrel life friendly. You can see slight accuracy degradation from throat erosion in as little as 700 rounds from a 7mag with a sporter barrel. .308 will often shoot several thousand before any accuracy degradation can be observed.
These are things to think about, and really only you can answer the question. If you are just starting out, and you aren't upgrading to hunt grizzly's in Alaska, the .308 will likely serve you well.