Hard one really.
My Brittanys have crates permanently available.
I have a 36" for the bigger and younger dog which is fine for him - he can sprawl, curl, bounce, sit, stand, move around and my WSS also uses that crate - sometimes they have squished in together. The other crate is 42" and for the smaller older dog, he needs to spend more time in there for safety reasons so I went for the bigger size. When "The Dog Formerly Known As Chico" arrived I decided on another 42" crate and he is swamped in it and has only used it for one night cos he is happier out in the kennel (where he has already settled to bed!!!).
Most springers would be perfectly happy in a 36" crate although some adult males may find it a bit restrictive, depends how you are going to ultimately use your crate and how long the dog will be in it.
HTH a bit