The concert ukulele, as its name suggests, is considered the gold standard of the uke world. Along with its bigger and smaller siblings, this instrument is known and loved for its tropical-inspired Hawaiian look and sound. Whether it's your first ukulele or your second, third or fourth, the concert size is one that any uke player ought to have in his or her collection. Any acoustic or acoustic-electric ukulele will be made from either laminated or solid wood. Denser woods like mahogany will give you a clear, guitar-like sound while spruce and other soft woods have a mellowing effect on the tone. Nato sounds sharp, loud and resonant—essentially the opposite of mango, which is quiet and restrained, with distinctive patterning that makes for a beautiful uke. Many players consider koa the definitive wood for the ukulele, so it's worth a listen if you want the most authentic Hawaiian sound.
You'll also find several types of specialty concert ukuleles to choose from, such as the metal resonator models. Just like the similar style of guitar, these ukuleles are built with a metal resonator instead of a traditional sound board arrangement. This has two effects on the instrument: first, it's just plain louder than a standard acoustic ukulele, and second, a resonator gives the instrument's sound a unique character. Other cool variations include Luna's banjolele (part ukulele and part banjo), the Epiphone Les Paul uke and several solid-top models with dual sound ports: one facing you and one facing the audience.
If you play professionally in larger venues or with a band, your primary focus might be on acoustic-electric ukuleles. You won't be missing out on any of the concert uke's character since they behave like a normal acoustic while unplugged, and they give you the option of plugging in to an amplifier when you need to kick the volume up a notch—or directly into your mixer at home for recording.
Most uke players will wind up owning a number of ukuleles over the course of their careers. If nothing else, it's very common to have one of each size to give you a choice of which sound you'd prefer to play at any given time. If you're looking to upgrade your concert uke or if it's the missing link in your collection, there's no time like the present to pick one out.