The biggest advantage of undermount sinks is that there is no lip or crevice where dirt tends to accumulate. You can just brush crumbs or wipe spills directly into the sink without anything getting trapped under the sink's rim. In addition to easing clean-up, these sinks also enhance the style of your kitchen. Because the edge of the sink is hidden, they offer a sophisticated, streamlined look to any kitchen's decor. Faucets are often installed in the counter behind the sink or on the wall.
Despite their practicality and style, there are some disadvantages to undermount sinks to keep in mind. Undermount sinks are harder to install than drop-in sinks and are often more expensive. They work best when combined with a waterproof countertop, because the edge of the countertop will be exposed to water. Undermount sinks are a great choice for solid surface and granite countertops, for example, but aren't generally recommended for laminate. Undermount sinks are sometimes installed with laminate countertops even though water damage is a potential concern; if you consider this option, make sure you find an experienced fabricator/installer. Since the bottom of an undermount sink will be an inch or so lower than a drop-in model, it may require more bending over whilte using the sink. Also keep in mind that because a custom hole is cut into the countertop for an undermount sink, it may be more difficult to replace the sink later -- so it's especially important to buy a good quality sink.