What are your objectives for calves in your operation?
I am commercially focused with the show ring as an added bonus. There is no reason that commercial animals can't go to shows and do well.
This is just my opinion on your calves and by no way am I an expert, but I believe you have a couple of very nice heifers that will be great commercial cows.
The black one to me needs some depth and guts added to her and I wouldn't change anything about hereford for the mama cow application.
I agree with a LBW Angus-- is a good choice.
With the Black heifer- I would go Red Angus-- There are lots of good Red Angus sires out there with LBW that will also bulk her calf up and give them some depth. The Red Angus really grow!!! Everything that goes across the scales at weaning you can tell at our house who has some Red Angus in them-- they are usually heavier. I haven't AI'ed any Red Angus for a couple years so I am a little behind on the newest sires, but I have had good luck with sires that go back to Cherokee Canyon or the Bieber Lines. I have a Bieber Make Mimi Durham Red cow -- and wow- she is the cat's meow!!
The Hereford heifer-- I am a Shorty person and there is where I would go with her-- you should get a great maternal and carcass focused animal. I would really recommend using a Waukaru bull from their string on the Hereford.
Thanks EF