Colin Chapman, famous maker of Lotus cars, had a mantra - ‘Add lightness’. That was why his cars are small, fast and handle well.
At the other end of the spectrum 4WDs can benefit from lightness as it will help with performance, economy and handling. Unless you specialise in fording deep swift rivers or towing large boats, in which case the opposite applies!
It should also reduce brake and tyre wear, allow suspension, engine, and transmission parts to last longer, and make it nicer to drive. So, if you are not aiming to drag the world behind you or cross raging rivers, leave extraneous stuff in the shed. Not the spare wheel! Or the jack and maybe some water, a blankie and a muesli bar. But you know what I…