I think, and I tried to express that with my post, there is no one ideal license. It completely depends on the situation.

If, like QT, the library is your whole product and you do not depend on the community for contributions, then GPL is great. It forces vendors of non-GPL software to acquire a commercial license, while open source projects can use your product without restrictions.

If it is not your core product and you want to encourage community contributions, BSD and MIT might be the license of your choice. You cannot prevent other companies from using the software, but neither are you prohibited of using any community contributions in your product.