My working cocker is docked. The breeder is a game keeper. Most of the litter were pre booked to working homes (bitch had two extra pups than anticipated), but you have to dock very early (after just a few days), so ours is docked, as he didn't know which pups would go to which home. We don't work him but do take the training seriously.
To be honest, there's hardly any length off his tail, hardly a third, and the damn thing never stops wagging.
He's a joy, and not at all mad or busy, just very gentle, timid and loving. Loves to please so easy to train. Currently not being walked at all as he's got a broken leg but he's coping well with extra training and cuddles.
I have a Springer too, he isn't mad either, but definitely bolder. Both will take as much exercise as you can give them but are very chilled in the house. They will follow you everywhere though, even to the toilet and the bin.
If I had to chose again, I would have another working cocker, DH would say the Springer.