I'm not sure it is. My intuition (Brazilian living in the UK, with lots of friends and family from or in Portugal) is that it's somewhat bigger but it's still close to 100$ interchangeable and understandable across speakers of either. Most Brazilians who have trouble understanding the Portuguese is because of accent, not language. Of course it helps that all Portuguese speaking countries have an orthography unification accord, and the grammar is pretty much the same.