You would first need to establish what is meant by ‘durable’, as people often have different definitions. Then there is also how a product is engineered - the manner in which separate materials and components are combined.
With a lot of the products you mention and have been on this thread, the designs were very different to today.
One of the properties of plastic is its ability to return to its original shape once a load has been removed, which gives it a natural return of energy. So if you dropped an old Nokia on the floor, the many layers of plastic would absorb the kinetic energy, temporarily bend, then return to the original form.
Metals that have been used in recent times don’t have this advantage, particularly aluminium. What you gain with Apple’s unibody in terms of rigidity, volume and weight, you lose in permanent damage when an accident does occur.
But this is a topic that could go on forever because there will always be benefits and drawbacks. Just because plastic is hard doesn’t mean that damage will be insignificant - it can come down to the type of plastic.
Just compare polycarbonate to others. Apple use poly for many of their early-2000s products, and it was driven largely by aesthetics. In practice, it cracked easily and was weakened by constant exposure to heat.
What we’ll discover over time is that, while yes titanium does have some benefits in strength to weight ratio, the decision to move to it will have also been driven by marketing. And the general structure of the phone isn’t reliant on this external titanium frame because the internal frame is still made from aluminium.
There are few clear answers.