(MONEY Magazine) – Smarter and slicker, the new fliptop and notebook computers are also more affordable. This year, worldwide sales are expected to hit 3 million, up 38% since 1989, says Dataquest, a Silicon Valley research firm. Barbara Bush taps away on a GRiD portable. Walter Cronkite works on a Compaq. Here's how to tell which one is right for you: -- Software. Most laptops are IBM-compatibles to run such favorites as WordPerfect and Lotus 1-2-3. -- Memory. Most IBM-styles now boast 640K of random-access memory (RAM). -- Speed. If you're a demanding user -- say, a C.P.A. -- get 16 megahertz or higher. -- Storage. A typical laptop floppy holds 720K or 350 double-spaced pages; most hard disks stash at least 20 megabytes or about 27 times that. -- Power. Batteries commonly last three or so hours. MODEL PICKS: Tandy 1500 HD. Just released, this six-pound notebook offers a 1.44-megabyte floppy drive. The 20-megabyte hard drive stores about 10,000 pages, and the NEC V-20 chip runs at 10 megahertz. RAM is 640K. Price is $1,999. Toshiba T1000SE. This one-floppy, 5.9-pound machine has a 9.54-megahertz 80C86 chip. The disk holds 1.44 megabytes. Price is $1,699; discounted to $1,100. Bargain hunters might scan the older 6.4-pound Toshiba T1000. Sharp PC-6220. This trim 4.4-pound model has a high-resolution VGA screen (Video Graphics Array) and a 12-megahertz, 80286-class chip. The hard disk stores 20 megabytes. List is $3,999; discounted to about $3,000. Data LP320 Laptop. This is a full-fledged 80386, speeding along at 20 megahertz with a VGA display and a fast, 43-megabyte hard-disk drive. Trade- offs are a hefty 19 pounds and 1 1/2 hours of power. Order from Dataworld (800-736-3282) for $2,665. Outbound Systems of Boulder, Colo. (800-444-4607) offers an alternative to Apple's misbegotten 16-pound portable. The Outbound weighs nine pounds and costs $2,999 with a 1.44-megabyte floppy or $3,999 with a 40-megabyte hard drive. A dealer removes two Read-Only Memory (ROM) chips from your Mac and sticks them in the laptop. Last, consider the Tandy WP-2 word processor. It can't run IBM-style programs, but it's ideal for frugal note takers. Cost: $350 list, about $300 discount.