Royce Da 5′9″ Prefers Flow Over Subject Matter

In an audio interview from the book "How to Rap" Royce Da 5'9" says he favors an ill flow over subject matter. Personally, I’d prefer a mix of both but if I had to choose it would be flow. Take for instance Nas. He raps about similar things in every song but his flow is disgustingly good. What some artists lack for in lyrical ability, they make up in flow. But some people's lyrics get lost in a bad flow. Interesting debate. Any Opinions?