The difference becomes demonstrable when arrogance makes you ignore emerging threats and opportunities in the market. They say, "The bigger they are, the harder they fall". So, if you let confidence blind you; you are actually being arrogant.

I do not think 37signals or Jobs is blinded by their confidence. Though one could easily claim Jobs confidence led to his downfall in 1987. He even explained this at the commencement speech at Stanford (I think).