If you want an ultralight gun, then go with .243. You already have a mountain rifle in 7mm, go with something different. I have a Kimber 84 Classic in .308 and if you are worried about recoil and your wife wanting to shoot it then you need to go .243 for sure. Not that the recoil is bad, but if its a concern then thats just my advice. I would take .243 over .223 every time, 10 out of 10 times for a hunting rifle.

If you ARE interested in .308 I would consider getting the 84 Classic like mine just to gain those few extra ounces. Still an ultralight by any standard. Mine has a low magnification Leupold and it is very pleasant to carry in the woods.