It's a personal decision, but I'm in the camp of not having then castrated unless there's a medical reason.
I've had male show type Cockers for 29 years and they've remained entire unless there's been a medical reason. In fact 29 years ago when I got my first Cocker, then his half brother 2 years later, castration wasn't even routinely discussed when you went to the vet, let alone pushed like it is nowadays.
My first one ended up being castrated when he was about 10 because he had an anal adenoma and an enlarged prostate. Both conditions were benign and castration + removal of the adenoma were suggested and done. No further problems apart from his coat changing for the worse and a battle to keep his weight down for the rest of his life. William, now 12, is also castrated. He had an undescended testicle which failed to put in an appearance, so I waited until he was 15 months old to give him time to mature and then had him castrated. It ruined his coat and I battled with his weight until I changed his diet to raw a few years later. I have to say that he's the least robust and most unhealthy Cocker I've ever had, but of course I've no way of knowing if any of his problems are linked to being castrated or not, so I don't spend time dwelling on it.
I can honestly say that none of my male dogs has marked indoors apart from a bit of juvenile confusion over a real Christmas tree by 13 month old Sam! None has ever run off after a bitch, or pined, whined or exhibited any other sexual behaviour or frustration around bitches. Josh went through a tedious teenage phase of humping the legs of other dogs (male and female) and people's legs, but he soon outgrew it and stopped as he matured and went back to just humping his favourite toy!
Castration prevents testicular cancer and decreases the risk of benign prostate problems, but increases the risk of prostate cancer, bladder cancer, hemangiosarcoma and bone cancer, although the last is mainly in large breeds. The risks are still relatively small, but they are higher in castrated dogs than in entire ones. Early castration, before physical and mental maturity, is linked to an increased risk of joint problems and a tendency to leave dogs stuck in a permanent puppy mentality.
Please don't be rushed into a decision j.edward321. Take your time, do some research and go with what you believe is best for Finn and for you