So would you recommend a 2008 over a 2004 or is a "good" 2004 just as good to buy?
The 2008 version incorporated a number of small changes, and was essentially the last update until the end of the model. If your budget goes to a 2008 or later, then my advice would be to seek one out with the lowest miles and best service history that you can find. However anything from 2004 onward has power screen as standard, additional heat shielding, and swing arm pivot changes to improve high speed stability, and would be a great bike.
In summary, and in my opinion...... 2004 or later would be great, but 2008 onward would be even better.