(FORTUNE Magazine) – My big mistake was starting a digital journal recording my most intimate thoughts the very week I began testing the lightweight portable computers known as subnotebooks. I wanted to compare the newest model of Hewlett-Packard's reliable OmniBook, the 800 CT, with IBM's popular ThinkPad 560, a slender, elegant machine known for its dazzling 12.1-inch display. Having carried the HP on a two-week trip to Thailand, I switched to the ThinkPad for a grueling itinerary through India, the Philippines, and Singapore. That's when the trouble started.

The machine worked just fine--actually, they both did. The problem was the ThinkPad's gorgeous color screen, which caused heads to swivel as if Salma Hayek had arrived, topless. Once my neighbors at airport lounges or aboard planes started gawking, they couldn't help but notice what IBM's bright screen sometimes displayed--my journal, written to help navigate midlife's whiter waters without needless investment in psychiatry. The contents of this graybeard's diary are none of your business, but apparently it's hot stuff: More than once I saw an onlooker's face melt into fascination, followed by a quick, guilty glance in my direction, as he or she considered reaching over to hit the PgDn key.

For anyone who works with confidential information, the very sexiness that has won the ThinkPad 23% of the $3.3-billion-a-year global subnotebook market is the best reason not to buy it. Why tempt strangers, perhaps competitors, to ogle your private stuff? This highlights a paradox at the heart of the portable-PC business: People often buy sexy technology they don't need.

Usually shoppers go overboard on features. Many of the portables sold are awkward behemoths outfitted with loads of unnecessary gear, weighing a tendinitis-inducing eight pounds or more. You see owners of these deluxe machines at airports all over the world, rubbing their shoulders and swearing.

People who opt for subnotebooks at least get the heft question right. Laptop computers are designed to be carried, so lighter, by definition, should be better. To slim the machines down to five pounds or less, subnotebook manufacturers replace internal CD-ROM and floppy drives with plug-in units that can be left behind on trips or packed in a suitcase. They also work hard on miniaturization. This is expensive and brings the prices of subnotebooks up to the same level as those of bigger, fancier models. Experienced computer users who travel frequently, presumably the most knowledgeable buyers in the market, willingly accept the tradeoff.

The IBM ThinkPad 560, which has cornered the market in subnotebook glam, is arguably the most intelligent variant of the "Gimme the best you got" mentality. The gaudy display is so big that the computer's case has room for a wrist rest and generous keyboard without resorting to the tricky "butterfly" folding keyboard design of IBM's previous model, the 701, whose footprint was 25% smaller. By IBM standards, the 560 is relatively inexpensive. Fully loaded--with a 166-megahertz Pentium processor, 16 megabytes of RAM, a 2.1-gigabyte hard drive, plus external drives and a port replicator that permits one-step plug-in for all your cables--the 560 lists for $4,977. Travel weight, with one battery, PC card modem, and power supply, is 4.3 pounds.

Quibbles: The ThinkPad is a tad dainty. After only a couple of weeks the case had warped, and two of the three absurd little doors covering its various plugs and outlets had vanished. The TrackPoint device, which replaces a mouse with a wee nubbin protruding from the keyboard, requires persnickety micromotions of the index finger that I find annoying. But hey, some folks love it. Also, every 560 I've seen suffers from a pair of smudges on the screen, evidently the result of rubbing against the TrackPoint's two buttons when the case is closed; IBM claims to have fixed this flaw in more recent production. Bottom line: The ThinkPad is a near-perfect machine for obsessive-compulsives with small fingers and no secrets.

The little-known HP OmniBook 800 CT, by contrast, is right for almost anyone. Smaller than the IBM but half a pound heavier, the OmniBook is more rugged and fits easily into a briefcase; its 10.4-inch screen is just big enough to please the eye without inviting onlookers. The machine is not perfect: It lacks a wrist rest, and my HP's batteries drained far too quickly, in less than two hours. And loaded up, the OmniBook costs about 10% more than the ThinkPad. But in other ways this PC meets or beats the 560 on count after count.

Why can't HP sell more of these wonderful machines? Richard Archuleta, head of HP's mobile computing division, explains why HP ranks only seventh in subnotebooks. Reason No. 1 is the idiosyncratic OmniBook mouse, a rectangular minimouse-on-a-stick that pops out of the PC at the touch of a button. HP's mouselet is peculiar, but to my taste it ranks second only to a touchpad--a gizmo neither HP nor IBM subnotebooks offer--as the best pointing device yet for portables. Mourns Archuleta: "Our mouse is scary to people who haven't used it." The second barrier is HP itself. Famously populated by engineers, this is a company that, according to company lore, would advertise sushi as "cold, dead, raw fish." Until recently, OmniBooks played second banana to HP's calculators in a business unit that produced both; now laptops stand alone, and Archuleta plans to push them hard.

Life is all about tradeoffs. The OmniBook is practical, the ThinkPad is cool, so take your pick. Whichever you choose, remember that prices of portable PCs start to plunge dramatically just three months after initial release, permitting great savings on older machines. Since these products are past their infancy, they're becoming lightweight bargains.

INSIDE: Why logging on at Bankers Trust isn't a private affair, page 218...A brand-new way to write, page 219...Alsop on the joys of digital photography, page 220...