2cm granite is generally less expensive, but performs the same as 3cm. That is, both are beautiful, durable, antimicrobial and will increase the value of your home. Esthetically speaking, the 3cm stone is thicker and therefore looks better, and the colors available are typically more exotic. You can get both 2cm and 3cm granite vanity tops relatively cheap at Lowe's.

With a mitered edge, the line tends to be hidden on the corner transition. Some of the quartzites are pretty expensive so the 3 cm might cost significantly more (though the fabricator will charge something for the labor of making a laminated edge and probably even more for a mitered edge so that offsets the extra cost of 3 cm unless you go for a 2 cm edge). Our quartzite is laminated, not mitered and the fabricator did a good job so I mostly don't notice the line. Only when I look for it. You don't need to do a laminated edge even if there is plywood under it. Two friends of mine did a 2 cm thin edge. One used a simple trim molding of wood matched to the cabinets to cover the edge of the plywood. The other left the plywood edge uncovered - I know because I put my head under the counter and looked into the shadow for it. If I was doing it, I'd probably cover with a trim piece because it would bother me, but only someone very TKO who looks for it would notice if you didn't.

"I have also been told that 2 cm is rarely used here anymore." and ..."oh, those over there are just 2 cm so don't bother looking at them." Not really. 2 cm is pretty much the standard on the west coast. I live in the very northern part of San Diego County and have been looking at granite for about 8 months. It turns out we live in Granite Yard City; there are at least 6 granite yards within 5 miles of my house and another 8 or so just 30 min. down the road towards San Diego. Lucky us, the closer ones seems to have a better selection. In any case, about 95% of what we've seen has been 2cm. The place I linked above is absolutely the exception in offering only 3 cm. In the end, our choice was made because we liked this outfit's work, not the thickness of the stone. There are benefits to each choice, but personally, I could readily go either way. I did see a 2 cm quartzite I loved, but it was pricey (!) and we would have needed 2 slabs to be sure there was enough to cut for the extra thickness on the edge. sigh The place we went with charges per square foot and they keep the leftovers. Had the quartzite people offered that, we would have seriously considered it. 2 cm or 3? Don't worry about it, just find one you like.

No, not if it's done properly. If the front edge is 2cm, there is no need for a sub top. If the front edge is 2cm with a 2cm build up, the build up can continue around the sink edge so no sub top will be visible. Here is a 2 cm top with a built up front edge with no build up at the sink: