Everything said so far is true. If you need just web browsing and pop3 email, netbooks are fine. Cheap, light, long battery.

If you need to run a full suite of business applications and want a variety of connectivity options, get a regular laptop.

There is a third category of small, powerful laptops with long battery life. Some of these, like the Lenovo X200, can run ridiculously long, up to 16 hours, when equipped with solid-state drives and when running in power conserving modes. A well equipped one starts at over $1500 and can cost much more.

Worth considering are the Dell Latitude E5400 and the Lenovo Thinkpad T400. These are both under 5 lbs., 14" widescreen, lots of power features, and great battery life. Also either can be had for less than $1000 in basic configurations (that includes Core 2 Duo 7xxx series processor). Both can also be configured with solid-state hard drives and have plenty of docking options.