Too much milk can be a problem.Perfect udder size and teat size are important plus having enough maternal traits to breed back on time and raise a stout calf.I have seen many cows with clubby background that are beautiful to look at but cant raise a calf and cows with same breeding that do great.Some of the best club calf mothers are the right kind of Angus that have 1/4 maternal Sim/Maine/or Chi and have never been near a showring.Big boned,hairy,small framed cows ,that have giraffe necks that some call front pasture type or donor quality usually don't last long but I have seen exceptions also that are great producers so in answer to your question good cows generally have great mothers regardless of sire.EPDs for milk production don't mean much as the cows with high numbers can milk too much and average numbers are about right.