We have five cocker spaniels, one show type and four working strain.
A very wise and renowned Cocker man told me that “the natural cycle of a spaniel is to hunt, flush, chase, catch, kill and eat. We ask a great deal of our dogs to break that cycle at flush and to bring their quarry back for us to eat!” Peter Jones.
I would say its all in the breeding. Not all working cockers are bonkers and want exercise all the time and not all show cockers are slow or have off switches! My show type at almost 10 (and unwell at the moment) is hyper most of the time, as a pup she was on the go from 5am to 11pm if I allowed it. The workers I have found to mostly be easier to train but have one with the prey drive of an Exocet missile! That is, shes fast with explosive energy making her hard to catch if she decides to chase and that is her biggest thrill in life!
The show type does not, will not and cannot retrieve but that her line - the breeder warned me as such before I collected her. She’s been to some of the best trainers there is and left them bewildered or bemused! Friends with show types have dogs that do retrieve but thats not the reason for having their dog(s).
My show type has worked five seasons on a shoot and is a great beating dog - shes a game finder, flushes then comes back to tell me! She is stubborn, obstinate, disobedient and only interested in whats good for herself but also affectionate and very pretty!
The workers are a different league in intelligence. They can open crates, stairgates (we now have locking stable doors throughout) and unless kept mentally active will get up to all sorts of mischief, often destructively so.
Show types need to be groomed. Workers need mental stimulation. If you are looking to have a well trained dog I would suggest finding a breeder than can demonstrate the attributes of the pup you are looking for - they should be happy to show you footage of the dam retrieving (sire influence whilst important its the traits from the dam you should look for) and that should be under control with no running in!
Good luck in your search
Jayne