if they were mine, I would consider their endpoints. Without seeing them in person, I think its hard to gauge what they look like. The top heifer is one I really like and when i blow the pic up I think she has enough belly, not a lot but enough. I think shes a heifer if fed right will probably be your best heifer at the last show. The amount of hair worries me on her belly, meaning she might not be quite as deep as I think. But shes a heifer i believe if fed a high fiber diet under the right management could be a really good fat heifer once she matures.
The second heifer is one i think is the better jackpot heifer. she has a more mature look with a big sweep to her belly. From the pic and looking at her cannon bone I think as a fat heifer she might run out of steam. As a jackpot heifer, i feel that belly and neck will carry her a long way. I think you just need to decide if you want to put all your eggs in the early basket or the final basket.
Another thing i'd bring up from the top pic is, how much base does she have? She is standing very narrow in the pic and I assume its just a bad time to capture the photo and not like that in person. I think the biggest thing on heifers that we cant see in the pic is soundness. Id move them around and they if they both have enough cushion and if they hit their stride. Sound cattle are easier feeding cattle
I think they are two different heifers and a hard decision.