Just like GTmike said. Unibodies are cheaper to produce. Just like front wheel drive. Not better, cheaper.
You never hear of anyone restoring a 1982 Chevy Celebrity, do you? Unibodies are actually called "disposables." That is a corporate design and sales term. In Detroit at GM, they lovingly called the Unibody car teams "disposable As, Xs, and Ns"
Long term durability, gotta be a frame car. Its true, today's unibody cars are engineering marvels. You take tin foil, mold into a computer generated shape, and it results in remarkably strong construction. Unfortunately, once its been smacked, you've altered it from the computer generated perfection. Sometimes its fine, sometimes its useless. Or in the case of many early unibody cars, they were worthless to start with.
Another thing to consider. My 66 Bonneville is of course a body-on-frame design. The body is currently suspended from four ropes in my garage so I can restore the frame. Try doing that with a unibody car, even WITH subframe connectors and you chance misalignment or even collapsing. I would challenge that my Pontiac's body alone is more rigid than any unibody car from the 90s. Of course it weighs 4300 lbs, too
