Well, I am the opposite of Sohcrates - I recommend the internal drive be DVD. That is what I use most on my laptop - especially when travelling. Movies are big in that mode. Burning CDs has never been a requirement on the road.
So, I use and external burner - and have ALWAYS used external burners on all system for the past 8 years! They used to be SCSI and now are Firewire - and buffer underruns, coasters, etc., are never part of the scene.
So, I leave my external burner at home when I head to the airport. DVD is much more useful on a long flight than a burner is.
I have three external Firewire burners and one USB 2.0. All are excellent - no coasters.
And if you can get it, a 3-way combo would solve all problems.