LAST EDITED ON Jul-28-15 AT 12:16PM (MST)[p]I have a couple customs and in my opinion, the cartridge you choose is not as important, especially between those two, as how comfortable the rifle is going to be in the field.
If you are not into shooting at deer and elk so far away that they don't know that they are being shot at, go with a lighter to carry rig and you won't regret going heavier as i did with my first, purpose put together rifle. It now stays in the safe most of the time because packing the thing around just got old.
Just because a loaded rifle-scope setup only weighs 7 pounds ready to roll, don't mean it can't shoot itty-bitty groups and lights out in the field.
BTW, for a light weight custom, between the two "cartridges" given, i'd go with the 300WSM.
Joey
"It's all about knowing what your firearms practical limitations are and combining that with your own personal limitations!"