While the world of kitchen sinks is large and varied (there are at least 10 basic types), for most homeowners doing a kitchen remodel, the field narrows down to two: drop-in or undermount sinks.
At one time, drop-in sinks were the only game in town. Even after undermount sinks hit the residential consumer market, they remained exotic and premium for a number of years—more difficult to install and more costly to purchase. Now that professionals are just as comfortable installing undermounts as they are drop-ins, and prices of undermount sinks are more competitive, the choice is that much harder.
Drop-In: Drop-in sinks, the most familiar type and still the most popular, are also called self-rimming or top-mount sinks. All terms mean the same thing: sinks that have a visible lip around the perimeter that rests flat on the counter. The sink drops straight into the countertop cut-out and the lip holds it vertically in place. Controlling horizontal movement are hidden metal clips that clamp the sink to the counter.
Undermount: Undermount sinks install from below the counter. This sink does have a rim, but the rim is not visible as it attaches to the bottom of the counter.
For More Countertop Space
Which one is best at preserving countertop space? With undermount sinks, the countertop extends all the way to the sink—even a bit more. If you're tight on room and need every possible square inch of counter real estate, undermount is the way to go.
One type of drop-in sink that rarely gets mentioned is the drainboard sink, which is like a drop-in sink on steroids. Usually, one side of the rim extends 8 to 10 inches to form a drainboard (thus the name) or in fancier models, a cutting board and food prep area. If you're tight on counter space, this counter-intuitive move, adding more sink rim, might actually be more economical on space.
For Easy Cleaning
One of the more frustrating things about undermount sinks is the gap at the top of the sink, where it joins up with the counter. While this gap is filled with a bead of silicone caulk, it's not 100% filled. A gap remains and this gap naturally becomes a magnet for food build-up. Greg Fox at Fox Granite Countertops recommends digging out the caulk on undermount sinks "every three to five years."
With drop-in sinks, all working areas of the sink are visible and accessible. However, it should be noted that the small, visible seam formed by the lip and the countertop can build up gunk, as well. The only difference is that you have better access and more visibility when cleaning the drop-in sink.
For Easy Countertop Cleaning
The clear winner in this category is the undermount sink. In fact, ease of cleaning is the number one selling point of any undermount sink. Because there is no lip to form an obstruction, you can swipe food particles directly off the counter and into the sink.
Drop-in sinks' rims are too high to allow this. Not only that, the angle formed between the rim and the countertop can build up with gunk.
For Easy Installation
Homeowners can easily install their own drop-in kitchen sink. As long as a cut-out in the counter is already in place, these sinks can be installed in less than 1 hour.
The Least Expensive
In terms of both materials and labor, drop-in sinks are cheaper.
For example, a drop-in Kohler Brookfield Drop-In Cast-Iron 33 in. 4-Hole Double Basin sink can be purchased at Home Depot for about $249. Its undermount counterpart runs around $418.
In terms of labor, Greg Fox estimates that the cost of installing an undermount sink is higher, but only marginally, about $50.
For Better Choice of Countertop Materials
Undermount sinks can be attached to all types of countertop materials, except for laminate. The laminate isn't the issue; it's the underlying base of particleboard or MDF. MDF is too weak to hold fasteners that have no backer (i.e., a bolt, nut, and washer) arrangement. Drop-in sinks can be installed on all types of counter materials.
For Better Resale Value
Whether your kitchen has a drop-in sink or an undermount sink will not, by itself, change the resale value of your home. Resale value's "needle" is affected more by major changes in your home, such as additions, whole-house flooring, or finished rooms than by single elements such as a kitchen sink, bathroom vanity, or choice of paint color.
As one building block of a highly valued "designer" kitchen, the undermount sink can be said to impart higher value to potential buyers than a drop-in.