Difference in brake cables?

OK I know what a MTB cable is. But my question is on the difference between road bike brake cables. Specifically the ends.

In stock I have some road bike brake cables for my road bike. They sort of look like a large derailleur cable end. A cylinder with the end is squared off. But on the touring bike, same thing except the end is rounded.

What are the difference between the two (besides the ends ;) )? Are they interchangeable?