How many portfolios? Sketchbooks, notebooks, a book of the end results, and a digital portfolio are all good to take along with you to a freelance design pitch or an interview. Some of my most recent work is digital; websites, social media designs, eShots and therefore work best displayed on my iPad rather to my printed book.
Sketches are good to show off your conceptual thinking and creative ideas, showing the work involved to conclude the final outcome. This applies the same in terms of an illustrator with animation skills, or a cross-disciplinary practitioner. It is difficult to incorporate several styles in one portfolio.
There is lots of useful information for designers and illustrators inside including inspiring ways of displaying your creative portfolio. The book can be purchased here.