(MONEY Magazine) – John F. Kennedy may not enjoy a reputation for fidelity, but when it came to his briefcase, his commitment knew no bounds. For evidence, look no further than the lone briefcase that he kept from the 1940s to the halcyon days of Camelot--a black alligator Hermes case his father had bought him.

Such is the passion that many feel for their cases. And while it's uncommon for a briefcase to last a lifetime (Kennedy's case reportedly needed regular repairs), choosing the right one can mean the difference between carrying it for two years or 10.

Yet what you'll likely buy today is a far cry from Kennedy's Hermes. Sales of boxy hard-sided leather attache cases have been collapsing over the past 10 years. Instead, the fastest-growing segments of today's briefcase market are casual bags, laptop cases and backpacks, and the designs are more unisex than ever. A single case with soft, expandable sides can serve as your briefcase, laptop carrier and even your overnight bag.

That's good news. The other good news is that you're getting more for your money, as briefcases come in stronger materials and carry longer, often lifetime, warranties. But the problem is that with well over 100 manufacturers, there are more cases to chose from than ever. Pick a sub-$50 bargain bag, and it may break or tear, or even discolor your clothing. It may also be, well, short on aesthetics; the $29.95 Heritage attache we saw at Staples featured a vinyl exterior and a "simulated pigskin" interior. No, thanks.

Here, then, is how to get a handle on what's out there. All bags mentioned, except for the Lands' End case, are widely available at luggage or department stores.

The casual case

Boxy attaches have lost ground because people are stuffing more into their cases, and soft, expandable leather, nylon and canvas cases let them do just that. These also have more pockets for accessories like cell phones.

One of your most critical decisions, then, will be the choice of material. There's little question that nothing beats the look of high-quality leather: If you're looking to impress, it's the only way to go. Yet for road warriors who push their cases to the max, the advent of ballistic nylon is a godsend. Cases made of this material are relentlessly sturdy and far less expensive than their leather counterparts. Poke a hole in it, and ballistic nylon "self-repairs," in industry parlance, as the weave closes around the gap. Plus, the material doesn't scratch like leather.

Even Marv Rosen, who has repaired briefcases in his Manhattan shop, Superior Leather Restorers, for more than 30 years for customers ranging from Ralph Lauren to Frank Sinatra, is a convert. He owns a ballistic nylon Tumi case because of its durability and the price. His Tumi, the 908 Expandable Brief, comes in high-quality napa leather for $365 and ballistic nylon for $225 (call 800-322-8864 for the nearest Tumi retailer).

We also liked the slightly less expensive Kenneth Cole Portfolio case (800-536-2653), which lists for $295 in leather and $100 in ballistic nylon and has plenty of room for files, a phone and other workaday flotsam. With any case, if you opt for leather, be careful about the quality and keep in mind that all kinds of leather are used for briefcases: calfskin, cowhide, goat, ostrich, alligator and pig, to name a few. (For more on leather shopping, see page 222.)

The laptop case

Once just a specialty bag, laptop-friendly cases are now the domain of highbrow luggage makers and outdoors shops. And today's laptop bag can serve as a briefcase and overnight bag as well, which offers another advantage: Since it doesn't look like a computer case, it's a less obvious target for thieves. Take Coach's cowhide Double Zip Organizer Brief ($496; leather only; 888-262-6224 for a catalogue or location of the nearest Coach store), which looks more like an executive case than a computer case.

While every laptop case offers cushioning for your computer, models made by a relative newcomer, Brenthaven, have raised the bar, so much so that Mobile Computing magazine recently picked Brenthaven's Computer Topload model (ballistic nylon only; 800-803-7225; $275) as the best at absorbing shock in a laptop drop test. Brenthaven cases also have a wide, well-padded shoulder strap that's more comfortable than most.

If these bags are out of your price range, consider Lands' End's $149.50 Ballistic Laptop Attache (800-963-4816; www.landsend.com). As an alternative, if you already have a briefcase you like, check out the Lands' End $29.50 Protective Laptop Sleeve, which can cushion a laptop when you put it inside your current case.

Finally, avoid any laptop case that leaves room for little else. For example, you might be tempted by the metallic glow of the Zero Halliburton, an all-aluminum case made from the same material found on the space shuttle. But not only did the heavy, inflexible model we looked at cost almost $400, after we put a laptop in, there was room for hardly anything other than a space pen.

Backpacks

Backpacks that double as briefcases and laptop cases are the latest rage, in part because they can be easier on your back. At the high end, Tumi makes a SafeCase Deluxe Computer Business Backpack ($495 napa leather; $350 ballistic nylon) that, aside from being one of the best-looking backpacks, boasts Tumi's SafeCase suspension laptop sleeve, which can be removed from its Velcro moorings to make room for more stuff. The pack has floppy-disk pockets, a front accordion-file section and comfortable shoulder straps.

Finally, when you're shopping for the perfect case, consider warranties. All the cases mentioned above come with lifetime warranties; you'll be taking your chances with anything less. Most lifetime warranties are limited to repairs such as defective seams or zippers. Any damage you inflict may require a visit to case restorers like Marv Rosen and his wife Thea of Superior Leather Restorers. Not that this isn't a pleasant experience. When asked why a signed Frank Sinatra photo hangs over the entrance, Thea explains that in the early '80s, as Sinatra was getting off a plane, he dropped his prized ostrich leather attache case in a puddle, soiling it, and had it sent over to the Rosens immediately. "I had to bring it back to life," she beams. "It's a shame I can't do the same for him."