It is normal that you and your son don’t like the same furniture or the same tastes about everything. But you have to listen them and reach an agreement.
Teenagers pass lot of time at their bedroom, and they bring friends at home. For this reason it is important to have a pull out bed, because you don’t need another bedroom if you have guests.
As they grow up, they use more cosmetic products and decoration. They will need space, so furniture, shelves or simplement boxes for managing space and save things will be necessary
If you and your son reach an agreement, you will see that it has been a good decision.
Trends are changing very fast, but if you choose a multifunctional bedroom, you will love it, and after, your son will decorate it at the way he want.