With no consistency in your cows, and beefmaster being one of the least consistently "typy" beef breeds, you may be getting a hodgepodge of different looking calves.
But otherwise, as mentioned by others, the red one has a lot of sheath. The brockle faced one looks more masculine and meaty in the front and the red looks more meaty in the rear... but it's hard to really tell from the pics which is the better bull. It may be the way the red one is standing that makes it's rear look better.
The Hereford bull does look short. It also makes him look long, which is good. If he's seven and serviced cows for five years without injury he might be the best choice.
Personally I wouldn't buy a bull to service five cows. Synchronize them and breed all of them at the same time and done. This way you get to choose a specific bull to complement the individual cow, but you can breed them all within a specific breed for more consistency. Sell anything that didn't breed or call the AI tech back to do it again. If one doesn't breed by then, sale barn her.