Hi,
The way I would present my work to clients is on the computer, therefore if there is a few quick and simple changes they would like to see its easier to implement on the computer than on a sheet of paper.
However if it is print work that you are doing then it is best to print out the final version before your client finalises the design as sometimes the colour on the computer can be different when you come to printing your work!
Hope this helps!
Stacey