My dogs are long dead, but I suppose my experience is still relevant.
I hunted upland birds so I selected for a breed that was efficient and competitive doing that. I had two English setters of slightly different breedings. I got the second 15 months after the first, so they were both certainly green at the same time for a bit. I just took them hunting a lot and put them on wild birds and they got things sorted pretty well, and both ended up being fine bird dogs, with one being quite exceptional (nothing I did--he was just born that way).
Two dogs, to me, are better because you can nearly double your productivity for your gallon of gas. One dog can only do so much. I preferred to run each dog around 2 to 3 hours a day, at most. So only having one would have been quite limiting. Most times we'd team up with a buddy and his dogs and 2 dudes and 4 setters were able to hunt for a weekend quite effectively. On a longer trip 6 or more dogs would be ideal so you could give rest days here and there.
There are other efficiencies. For example, it takes the same amount of time to take two dogs to the vet as one. Same time for a walk or a run. Sure, ear scratches are divvied up but really they are just doubled.
The largest benefit is those dogs will be each other's brothers. They are company when I'm at work or otherwise gone. They would play and wrestle and tussle with each other. I don't recall a single fight between them. They were great to each other.
Once my kids are a bit older I expect to have another brace of white dogs. Once I'm retired maybe more than two.