JR, you said they all give tons of milk. In that case, I stand corrected in my conclusions from the pics and info.
Here was my thought process in my decision on the cows. This is the same thought process I use when buying cows at a sales barn or on the farm. You said all 3 cows are just weeks from calving.
Cow #1 has no udder. To be 6 years old and have no udder whatsoever makes me think she is not a milker. To be just weeks from calving and still have nothing makes me think that even stronger. She is thin and not bellying up or springing in any way just a few weeks from calving. That is usually a sign of a cow gonna have a small, weak calf and not have much milk for it.
Cow #3 has just a tiny bit more udder. However, not springing nearly enough for cow that is just weeks from calving. She hasnt had a calf for a long time, she should be bellied up and bagging up quite a bit being this close to freshening if she is a real good milker.
Both of these black cows look like the kind of angus that will raise the 400-450 lb calves instead of the 600-700 lb calves you want out of your beef cows.
The white face cow looks like she gives considerably more milk than the others, but she shows almost no udder for a 8-9 year old cow. Cows that are heavy milkers dont have tiny udders like that just weeks from calving. Also, she weighs 1635 lbs. It is highly unusual for a cow that gives enough milk to wean 600-700 lb calves and freshen every 10 1/2 to 12 months to get that big, except in certain breeds. That is usually the sign of a cow that doesnt give enough milk or doesnt raise a calf every year for her to get that big.
The way you described all three cows, in your mind, and in my mind also, they are all cull cows. I believe they will make you money to hold until July to cull them. Good luck with your decision