I agree with you... Heston just doesn't look like he's done growing. He's all gangly and has a light hind quarters. Honestly, nothing about him made me want to keep watching his vid. He seems unimpressed with the jumping. Granted these are wee little fences.
As for Jethro, the paddle can be a concern on an eventer. Anything beyond perfect conformation will cause extra wear and tear. I'd have him vetted thoroughly. However, he is the better mover, even with all his fussing. He just seems more balanced. He also seems to have some interest in jumping.
It's hard to tell if either will be anything beyond a C level horse. They're both green. Though my bet is Jethro is athletic. He also has good classical movement, so he could easily flip flop between Hunters, Eventing and Dressage. Your daughter may not be interested in Hunters (though I hear that's coming to PC), but it's always good to think of resale should the day come.
Where does your daughter plan on going? Is she aiming for her C3 or does she want to go even further? Does she have another horse to rate on till her green horse is at the level she is at?
If your horse says no, you either asked the wrong question or asked the question wrong
And God took a handful of southerly wind, blew His breath over it and created the horse