Any time you buy anything, and you want to be reasonably systematic about the process, you examine all relevant options and choose the one that best meets your needs.

For digital devices today, one interesting point in any buying decision tree is whether to follow the branch that emphasizes power or the one that emphasizes portability. Desktop PCs have the most power, at one extreme, while smart phones have the most portability, at the other extreme. (Dick Tracy-type watches that let you talk with others and tap into information are still off in the future.)

If you want to split the difference between power and portability, you may be left with the decision of whether to go with a thin and light laptop or a netbook.

First some context. Until voice recognition becomes truly workable, any digital device without a physical keyboard, including smart phones, portable media players, and tablet computers, is better suited for consuming information than creating it (even factoring in add-on wireless keyboards that you can use with some of these devices). Further, if you spend a lot of time creating information, no device is as fast and ergonomically sound as a desktop computer.

Still, if you need to compute in different locations, whether on the road, moving around the office or house, or in various locations at school, you don't want to lug around a 60-pound powerhouse desktop PC or even a 15-pound "all in one" desktop PC that has a monitor attached to a keyboard with the processor and memory inside the same case as the monitor.

Portable computers these days fall into four main categories, from heaviest to lightest: desktop replacement laptops, mainstream laptops, thin and light laptops, and netbooks. Desktop replacement laptops have 17-inch and larger monitors, while mainstream laptops typically have 14- to 15-inch monitors.

Easier to carry around are thin and light laptops, which typically have 13- to 14-inch monitors and weigh around three pounds, give or take about a pound. Even easier to carry are netbooks, which have monitors that typically range from about 10 to 11.5 inches and which weigh between two and three pounds. Netbooks are the smallest and least expensive more or less fully functional personal computers on the market today.

I recently compared in depth a thin and light laptop versus a netbook to gauge the strengths and weaknesses of each. I went with models slightly to the higher end in each category.

For the thin and light laptop, I tested an Acer Aspire TimelineX with a 14.0-inch monitor, 4 gigabytes of memory, and a 320-gigabyte hard drive. For the netbook, I tested a Gateway LT32 with an 11.6-inch screen, 2 gigabytes of memory, and a 250-gigabyte hard drive. The Acer has a suggested retail price of $799.99, the Gateway $449.99.

Along with netbooks being smaller, lighter, and less expensive than laptops, the other main difference, including these two, is that netbooks don't come with a DVD drive and laptops do. To watch DVD movies on a netbook, you need to buy an external DVD drive or convert a DVD movie into a video file. The latter takes some technical skill--see www.ViDEOHelp.com for tips.

Both of the units I reviewed came with Microsoft Windows 7 Home Premium as their operating system and with feature-limited, ad-supported versions of Microsoft's productivity programs. The laptop was preinstalled with Microsoft Office Starter 2010 while the netbook came with Microsoft Works SE. Microsoft Office Starter 2010 lacks PowerPoint as well as macros and other advanced features for Word and Excel. Microsoft Works is similarly without advanced features and a presentation program. As an alternative, LibreOffice (www.libreoffice.org) is a well-regarded full-featured office suite you can download for free.

Interestingly, despite the laptop being larger, its battery kept its charge slightly longer, being a more powerful 6000mAh instead of 4400mAh.

As expected, the laptop's screen was easier to view, but the netbook was surprisingly easy to type on, better here than smaller netbooks I've tested. The bigger your hands and the worse your vision, the more likely you'll be bothered by any such netbook compromises yourself. I didn't mind the laptop's extra weight, but according to the anecdotal experiences of others, and trying not to sound sexist, women seem to value the lighter weight of netbooks more than men, with exceptions.

In short, if you value performance and ergonomics, a thin and light laptop is the better choice. But if light weight and price are more important to you, go with a netbook.