Subject to careful examination by the manufacturer, designed with high-performance raw materials, new tires ensure optimal safety. They are also quieter and more comfortable.
Used or new tires from an old stock are not recommended because it is impossible to know how they have been used or stored in the past. If they have been impacted against curbs, for example, they can burst at any time.
In addition, an old tire, even if not worn, is necessarily less safe than a new tire of recent manufacture. The tyre rubber ages badly over the years, which can lead to your tire bursting with the consequences that this can have! Do not risk your safety with old tires, even if they look okay.