I would definitely go with an internal. Samsung, Lite-On, and LG all make good DVD burners and they all run around $30. Plextor is considered the premiere burner but it's a lot more expensive. If you mean by professional, they will get heavy usage, I'd probably go with a less expensive one figuring with heavy usage you'll have to replace sooner than ordinary use. You could also google someting like "professional dvd burners" and see what you come up with. I would guess they'd be pretty expensive.
IGNORE the $30, forgot you wanted Blue Ray