If you haven't heard this debate, I encourage you to listen. Both sides are very cordial, but the exchange is quite lively. Christopher Hitchens is author of God is Not Great. Mark D. Roberts' most recent book is Can We Trust the Gospels? -- which, I might add, is an excellent book.
This debate took place on the Hugh Hewitt show and full transcripts are available.
The audio is compiled into one MP3 here.