Since you have a desktop already it would be better to get a laptop as your secondary system IME. Laptops are a lot more portable and totally self-contained. That said, for any serious work (or hardcore gaming if you're into that) a desktop is always preferable. Desktops are much easier to upgrade and tend to offer better performance at the same price.

I use computers all the time and type a lot. I've got both a desktop and laptop at work and use the laptop often, but usually with a full-sized USB keyboard and mouse. Typing on a laptop keyboard is a pain, ergonomically and otherwise.