The modern variable WILL do a lot of things that old 4x won't do. It will test your mounts better with it's greater weight. It will allow you to shoot with your head more erect as you mount it higher on the rifle. It will allow you to feel good about the extra lenses and moving parts you can count on.
Fixed 4x scopes are simple, lightweight, and rugged.
I have some variable scopes but only because that was all I could get. When I wanted a fixed 16, I had buy a 6-24 variable. I bought a 3-9 because it was available whilethe 6x I wanted was not. GD