Let's be honest. I only rarely use most of the features of my vehicles.

What's worse? A not in use bed, or a not in use back seat?

I have a truck, because I find it more convenient to have a truck bed anytime I need it, than to have to arrange to borrow or rent one. The bed doesn't get used often, but it's also a reasonable vehicle for driving solo or with one passenger; two in a pinch. Much better visibility than any other vehicle I have, too. Unfortunately, the single cab, 6-ft bed small truck market disappeared, and I got this one used with too big of an engine, so the mileage is poor... when I had a 4-cylinder small truck, mileage was better, but I don't drive that much anymore anyway.

But, I have lots of space, so I can keep a car for transporting a car pool in comfort, a PHEV with good mileage for longer trips that don't need anything special, a small truck for doing small truck things, and an old van with removed back seats that's fun to work on and can carry things that shouldn't get wet when it's raining. The van visibility towards the front is even better than the truck, because it's cabover, but visibility to the back isn't as good... None of those modern pillars that make it hard to see out the sides though.

> What's worse? A not in use bed, or a not in use back seat?

It's more "what's worse? A huge truck with worse visibility, alone, or a car that has better visibility, safety features, and less likely to kill someone in an accident, driven alone".

Obviously if the bed or the back set were the only swap, none of it matters.

And like... yeah there's the calculus of how often you use it etc.

> A not in use bed, or a not in use back seat?

A not in use back seat takes up far less space in a sane car than a pick-up truck with a bed.

> Much better visibility than any other vehicle I have, too.

At the expense of others. And good luck seeing a small child in front of it if you're driving in a moderately pedestrianized area.