Share third party libraries will save memory and you can control the version in the server installation. If you depend on a specific version you are able to use separate versions of the lib and depend the deployed application to it.
From a performance perspective there is no difference (exept the memory consumption).
App developers might prefer to have the tested version packed in the application. But if you pack JBoss libraries or EE libs in the application you might run into problems.
In any case it should be well considered what you do.