Both ways are good. I've found, that the more tunes i know, the easier it is to learn. After all, there are only so many licks available. That makes it handy playing in a session, where you don't necessarily know the tunes that are being played. However, the man in my life, tends to dissect tunes slowly, and really turn them into something wonderful. He can add a richness and depth that only comes from concentrating on an individual tune