I have a show cocker (2 years old), my parents have a working spaniel (soon 8 years old).
The difference in energy levels is massive - my dog is so easy and requires the daily walks (we don't have a garden) and 30-45 minutes of training/running/retrieving every day. We can skip the training for a couple of days without any issues.
My parents' dog has a massive amount of energy and is awful if bored/not exercised enough. It's hours of daily training, running her next to the bike and so on - on top of the daily walks. Training/exercise cannot be skipped at all as the dog will be awful - even at 8 years old.
My parents were dog sitting my dog for a while, and they were so shocked at the difference.
My dad spent a lot of time training the dog when they got her, so she's well trained. We didn't spend as much time as my dad, but our dog is pretty good - her recall is good, she knows quite a few commands and she's well-behaved in the house. Both were easy to house train.
Both dogs are lovely around other dogs, they never bark and they both love kids. We don't have kids, but the kids in the neighbourhood all know the dog and will run over to kiss and hug her. The dogs are always happy. But in true spaniel form, they are both velcro dogs. But none of them have problems being home alone.
I don't think the dogs are mad or crazy - something I've often heard about cockers. We went for a very good breeder and so did my parents.
Personally, I wouldn't want a working dog unless I was going to use it for hunting or other work. I wouldn't be able to keep it as a family dog as it's too demanding with regards to exercise. But that's just based on the experience I've got with the dogs in the family.