I like pup 6, though they're all super cute

Choose all of them :D

They are all cute and cuddly when they are small. But they are small for only a couple of months, then they pee on your carpets, chew your shoes, and the bigger one will fight the others for the food. And sometimes they grow larger than expected.

It's not the best idea to choose a pet in that early age.
When I chose my kitten, they were 1 month old, so big enough to see their personalities.
I didn't even asked about the gender when I made a decision, because I saw one bravest and friendliest kitten in a bunch and I realized that this is the one for me.
No matter how I wanted a kitty boy (neutering is cheaper), I chose a kitty girl and I'm happy with my decision.
If you need to choose one now, you can always ask to hold all of them and then just see which one feels "closer" to you heart (if that makes any sense to you).

First off:
PUPPIES!!!


Now, with that out of the way; I'm glad that you get the chance to test out their personalities first, since that's one of the most important. Just going by looks though, my pick would be number one because of his cute dark little nose (has a soft spot for animals with black on them, since all-black cats and dogs are less likely to get adopted, poor things) or number six (who sounds like he'd be a bit lazy, but still really cool).
For some reason number two looks like a loud snorer to me (can't explain why, it's just what my gut is telling me ), and, while that can be funny when you're awake, when he's lying next to or on your bed and you're trying to get to sleep at night...(is speaking from experience).