A round brush typically has a handle and a solid barrel on the end with bristles all the way around. A paddle brush also has a handle, but it's wide and flat on the other end with bristles on one side. These two very different shapes are ideal for different purposes.

That was a really good summary Lonewulf. I wouldn't have realized that a glossy paddle would have that effect, but it makes perfect sense.

The hairbrush feels so right whilst for me a Paddle just doesn't have the same effect.