To me, it's not very meaningful to compare the **default** settings of two completely different lighting models like the Specular and Blinn nodes.

But by playing with the node settings to bring the two effects closer together in some respects, the real differences between them become much more apparent.

On the left is Specular, on the right is Blinn.

There is one infinite light (left, behind camera) and one point light (centre, beyond the spheres). I used the Front camera.

I'm sure bagginsbill has mentioned these differences in the dim and distant past, perhaps as long as a couple of months ago. :O)

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)