I wish I could give you the measurements, but it has been a while. We had to go with one of the smaller diameter sinks, due to the cabinet configuration in our bathroom.
I was, however, careful not to get one that is too shallow.

Looking back on it, it is hard to believe that this (a Kohler) is considered one of the smaller sinks. Are people washing full loads of laundry by hand in the large ones?
babies? pets?

My advice is that if you stick with Medium, you will be fine. I prefer the counter space to the sink space though.

I don't know what size (sml) my sink is considered but I wanted a larger one than I previously had. It's 18" wide and almost 15" front to back. I like a larger width sink because of less water run-off from my arms/elbows onto the counter. My counter is 69" long.
Monica

I forgot to say that we want 2 sinks in the 7' vanity. Two sinks is a must. I cannot stand DH's toothpaste and shaving gunk in the sink. We had small sinks in our old bathroom, too small for me to wash my hair. I want something larger, but the large ones are really large.

I was wondering what people do with the really large sinks in the bathroom. Did they find them useful?

DH says, "who ever heard of anyone complaining that their sinks are too large?"