I have a laptop, desktop, and several PDAs and one PDA/Phone. To say that any one computing device is better than the other actually depends on the situation in which you intend to use it. For your purpose of reading PDFs at the gaming table, I would suggest either a laptop or a
Tablet PC.
The laptop is a great option, and based on current prices and functionality it's probably the best choice. They're cheap, portable, and have great battery life assuming you get one that's built for business applications and not for running the latest video games. The laptop is also the most versatile for day to day use as well.
The tablet makes a great device for taking notes and reading files. However, it will cost you more money than a laptop. Something else to note about tablets is that some do NOT have a built in keyboard, so if that's important to you then be careful when selecting one. They come in several different flavors from the laptop with an adjustable screen ala the
HP tc4200 to the "glorified PDA" of Motion Computing's
M1400
I personally use a
PDA/Phone as a DM and prefer it over a laptop for use at the gaming table. It keeps all of my PDFs, characters, Hyperlinked SRD, and everything else I need. It also fits in my pocket, weighs less than 8 ounces (226 grams), and makes for less clutter at the table rather than more. The handwriting recognition is very good for taking notes and there's a built in keyboard for long text entry. The screen is small, which is not ideal for reading PDFs, but it works well enough for me.
In the end it's all a matter of personal preference, but for me I have to echo Gothic_Demon. I use my phone.
