I'd say getting a dog from a breeder is often the better choice, but really depends on what you're looking for in a dog. But adopting from a shelter usually means that someone has gotten rid of that dog for a reason. More often than not, it's caused by the previous owner, but adopting a grown dog that's been treated wrong can be pretty challenging. They often have serious behavioral issues. They might be easily frightened, and a scared dog often reacts aggressively, something you don't want happening with children around. Also, teaching them new behavior takes a lot more time than it does with a puppy.
Personally, when we're selecting a new puppy, we go for certain traits that will make it a better working dog. That pretty much rules out dogs with unknown pedigree (if not only for the reason that to be able to compete the dog needs to be a registered breed), as to have a chance to get the best possible dog, you'll usually look for a litter with parents that have a proven record of being good working dogs. And also, to get the dog trained the way we want to, it's important to get to work from as young an age as possible.
Shelter dogs in my opinion are best suited for people who don't have children, and who have the time and knowledge to work through the problems their new family member might have. Especially if you just want a small couch potato floofloo, then shelter dogs are a good option in my opinion. Because most couch potato floofloos I've seen will be badly behaved anyway, just seems to me that the smaller the dog is, the easier it is to physically overpower it in different situations, making it easier to tolerate bad behavior from them. I know I'm guilty of this myself, our Dachshund enjoys far more privileges than any of the real dogs do.
When it comes to cats though, I would never care about it's pedigree. The reason I would get a cat would be that I would be living out in the country, and I would need a good mouser. Any barn cat would do in that case.
Good luck with your new puppy, Weimareners look pretty awesome, and I'm guessing the little one will make a good training partner for you in about a year or two. I'd take it easy in the beginning though, they have a tendency for hip issues and taking them on long runs on a leash at a young age can lead to the wrong kind of joint development.