In this category, plastic-based materials undoubtedly dominate (polycarbonates, polypropylene, and—though to a lesser extent—ABS), along with aluminum and composite fiber materials such as Curv (used by Samsonite in its Cosmolite® line), which, however, deserve a separate discussion given their very distinctive characteristics. These are the materials most influenced by technological progress and those currently most widely used by manufacturers in the industry.
Among the pros are certainly extreme sturdiness and impact resistance—characteristics that guarantee greater protection for the contents compared to a traditional fabric suitcase. Furthermore, thanks to special patented blends (see, for example, Makrolon®, used by the Italian company Bric's in its “Capri” line), these materials gain greater flexibility—a quality that, in the world of luggage, goes hand in hand with durability.
On the other hand, they can be quite heavy; however, thanks to technological advancements, new materials are becoming increasingly lightweight, keeping pace with their fabric counterparts. Hard-shell suitcases are also highly susceptible to impact at critical points (edges and corners), where the material is less flexible and can break easily; so if you want to buy an excellent product (the price will certainly be higher but it will guarantee superior durability) made of hard-shell material, make sure it has corner protectors.
Finally (and this is especially true for carry-on luggage, where external compartments are essential to prevent your pockets from becoming overcrowded), finding a hard-shell product with sufficient compartmentalization—that is, with a wide selection of internal and, above all, external pockets—is very difficult, with a few exceptions that are generally more expensive than average.
