will sink fit in base

I am trying to determine if a sink will fit in our new base.

We are replacing our kitchen cabinets, adding quartz countertops, and buying a new stainless steel undermount sink. We will have a 24 inch sink base, with an opening of 22 1/2 inches.

I have come across two sinks online that look like they will fit, one from Franke and the other Elkay. However, eventhough the Franke is LARGER, the specs say it will fit in our 24 inch cabinet, but the Elkay (smaller) needs a 27 inch cabinet. How could this be? Are there different mounting methods? How much space do I need to allow for mounting?

Franke
width: 21 1/4 in 22 3/16 overall
front-back 18 7/8 in 19 7/8 overall

Elkay
width: 21 in 22 1/2 overall
front-back 18 5/8 in 21 1/8 overall

Also, do I need to care about the "overall" dimensions? Isn't that just the size of the lip?

Any help would be appreciated.
Sue

A 24" cabinet is the outside dimmension...subtrack at least 3/4" on each side, and you are down to 22.5" and most of them have the sides inset a little. This puts you right at the dimmensions of the flange on the sink and leaves you no room to mount the clips that hold it in place. You need to find the interior width of the cabinet. Also, look at Kindred, they are good quality, and often a lot less than Franke. Don't even thing of a polished SS unless you plan to never use it as it will get scratched looking at it.