I've always felt strongly about having a printed portfolio in a hard-cover book. Nothing has presence when they ask
"Can we see your commercial work in the past years?"
And you lay them a stunning Hard-cover book with full page prints. I also take a laptop too but I prefer to present a book.
Not doing this for a living, I think a blending of both approaches is ideal. A great hard-cover filled with amazing, full page prints says high-end and classy, while also having a tablet or similar device lets you keep it more up to date with newer images, more images, and let's them see what it will look like on Facebook.
You can say "here is my uber-awesome-ZOMG stuff", here's my great stuff which I keep fresh all the time. And by the way, here's what it look like when you email it to people.