Its okay, all those fins can get confusing! =)
The royal blue female has better color, less red wash, but only one ventral.
The steel female has lots of red wash, and looks like no ventrals at all, but she has a better dorsal and better caudal branching.
It all depends on your goals and level of commitment: will this be a one-time breeding, or do you want to create your own line? Do you want to work on form first, or color? Personally, I'd pick the royal blue female.
There are lots of reasons for missing ventrals. They could have been bottom-dwellers as fry, and the bacteria on the bottom could have prevented them from developing. Or, they could have gotten munched on in the growout, and just never grown back. I'm not sure if there could be a genetic component?