The old timers said that if you have to bend down to pet a gun dog's head then it is a Spaniel. A Setter's head is where your hand rests when hanging down at your side. If you have to raise your hand to pet the head then it's a Dane.
Believe it or not, the size of a bird dog is one of the topics that can turn a discussion ugly. To that, and to the endless volleys of "best breed" arguments, I say that is why there are chocolate and vanilla and lots of flavors in between: pick what you like and don't worry about other people. It's enough for me to just focus on my own dogs as far as size and base my breeding goals on personal taste, what experience has taught me works, and what the avid hunters who buy my pups say that they are seeking. But make no mistake - size does matter.
As example,I have three dogs who are each 22" at the withers yet their weights are 50, 54 and 63 lbs. The 50 and 54 lb dogs are females and although the same height, the one weighing 50 lbs has the shorter coupled, more compact body that I prefer. That compact, short coupled body is more ergonomic because the topline remains level and tight during movement and therefore is more efficient with no body roll or extra motion that wastes energy. This translates into more bottom to hunt faster and longer without fatigue and quicker recovery for day after day of hard hunting.
Female,21" 48 lbs. Hunted til 13, lived to almost 16.
Male,22" 63 lb. Powerful and compact.
Cheers and Happy Hunting all,