Good for him!
I think that the speed would be more dependant on the computer's processing power and the graphics program rendering algorithm rather than the tablet itself. The one I have keeps up to my scribbles when I use it. You probably will want one that has more levels of sensitivity so that the pen has more functionality with direction, line thickness, etc. If you check out the Wacom website, they offer a wide variety of tablets for different environments/situations. I'm sure you will find one that would be suitable for what he intends to use it.