I would talk to the breeder lol I am a fan of letting the breeder make the decision 100% IMO.. it's so hard to choose even when you are there, because you are kind of HOPING that the way they are at that moment is the way they are MOST of the time.. which isn't always the case. (Like, that calm puppy sleeping in the corner might just be like that at the moment because he had been raising hell all afternoon and needed a nap lol)
I would see how the puppies play with each other, how willing they are to leave the group to come to you, how interested they are in toys/food etc.. and try to play with each puppy away from the group (I've seen pups that are a certain way with their litter mates but very different all by themselves)
Disclaimer: I work for Trupanion and love it/our policy! But I do not speak for the company or as the company.