I would say go for the runt! My mum had a runt of the the litter boxer, he was the last one left when she came to buy and she wouldn't have had it any other way, he was so loveable and a right character. I currently have Nelson an EB, we didn't get him from a breeder we came by him through someone trying to rehome so don't know his background although I believe he is fairly small for his age. He is weighing in about 26llbs and is 19 weeks old ( a bit less I think than the average weight, although my vet would not agree!). He also has tulip ears. To be honest he has a great character is very healthy and active. Whichever puppy you feel drawn to should be your choice, go with your gut instinct it is usually right!!