Undermount hands down for our upcoming remodel. Have had one for decades and would never go back to top-mount. I prefer the aesthetics of the undermount.

What ck_squared said. Pre-reno our kitchen had a top mount and I thought it was a pain to clean around it. Post-reno we have an undermount in the kitchen and 4 undermount bathroom sinks. No leaking problems, and I don't recall reading about any leaking problems on this forum. Does your mom have an undermount that leaks?

I much prefer the look of undermount sinks and the ease of cleaning around them.

No, I'm sure she's never had an undermount sink -- she just likes to think of reasons why things she doesn't like won't work :P

I would say I prefer the way the top-mount actually looks, but not so much that I really want to deal with scrubbing around the rim constantly.

(huh - sounds like my mom)

I have undermount and way prefer how easy it is to keep clean. It's also nice just seeing the counter and not any part of the sink. Then you have to decide between a positive reveal and a negative reveal.

I've never had an undermount sink till we re-did our kitchen a year and a half ago. I love it, and won't willingly have a top mount again. All our bathroom sinks are undermount and we've never had any problem with those. The undermount is easier to clean and I love the way it looks.

I think undermount is much more practical and easier to maintain. Other than having to scrub around edges and water collecting around the rim, over time overmount sinks have the possibility of the grout not holding and water that collects around the rim can leak into your cabinet.

I have lived with under mount for 2 months now and will never go back. It is amazing how much easier it is to clean and just generally looks neater all the time.

Undermount, hands down!

I have top-mount, but it's because we have laminate and wood countertops. If solid surface or stone, I'd go for undermount. You asked for pros and cons, and you've heard lots of pros. The con would be if you needed or wanted to change the sink... It would mean, I think?, taking up the counters and probably disrupting the backsplash.

"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 usually not filled flush to the surface. A depression remains, and this naturally becomes a magnet for food buildup. Citing this issue, Greg Fox at Fox Granite Countertops recommends digging out the caulk and replacing it on undermount sinks every three to five years."

This is nonsense. There is no "gap" between a properly mounted undermount sink flange and the bottom of the stone/countertop, nor a "depression", nor a "magnet for food buildup.". The silicone that does the waterproofing is squished between that flange and the stone bottom and isn't going to be dug out without dropping the sink. There is never any maintenance between an undermount sink and top when properly mounted. No gap, no depression, no food build-up.