Undermount sinks are preferred from aesthetic, hygienic and practical points of view.
Undermounts appear sleeker and more streamlined when installed underneath instead of on top. Most top mount sinks have a fairly thick rim (more than ½”) that is obtrusive. Undermounts look like a more premium offering.
Top mount sinks are sealed to the countertop with silicone, creating a bead that's tough to keep clean. With all the moisture around the sink area, this bead can promote bacteria growth and the eventual degradation of the actual silicone
Isn’t it nice to mop all that water on your kitchen countertop directly into the sink? You can only do this with an undermount. Also, it’s easier to wipe food prep remains directly into the sink when unhindered by a thick, top-mount sink rim.
To be undermounted to high pressure laminate, a sink must have an approximately 1” wide rim that is made from a resin, has been machined completely flat and meets the bowl wall at a sharp 90-degree angle.
Most stainless steel sinks don’t meet this rim spec because they have steel rolled rims – except for Karran’s Edge sinks. Their patented sinks are made of stainless steel, but feature a modified resin rim that allows them to be seamlessly undermounted in high pressure laminate and solid surface. As for model designs, the sky is the limit, apart from one caveat: double bowl sinks must have a lowered bowl divider. This allows for router bit movement between bowls during installation.
They use a solid surface seam adhesive to bond the wide rim directly to the back of the high pressure laminate. This methylmethacrylate, two-part, permanent set epoxy has been used for 10 years, and we have never had a seam failure. It is impossible for water to get through the seam in any way.
There are no special care requirements for undermount sinks in laminate countertops. Clean the laminate as specified by the laminate manufacturer; the same goes for the sink. Just because it is undermounted, it doesn’t mean that either component requires more careful maintenance.
This is most definitely a professional job. Not that it is difficult, but because it requires specialized tooling that a DIYer does not have, but a countertop shop would.