There is no difference between a "cow horn" spike, and any other spike bucks."Cow horn" is just a reference to the spikes shape.
I saw a cow horn a couple of years ago. It's antlers were at least 10 inches long, and wereperfectly curved as horns.
As far as spikes go, most of them are just young deer, that may be better bucks with time and nutrition. In looking at bucks, their body size, and the shape of their bodies and heads tell you much more about their ages, than the antlers do! In the case of the cow horn that I saw, he was as bigas any buck that I've seen in that area. He even had the classic "pot belly" of an older buck, and even though I did not shoot him, he was obviously a cull!