I have both an S-Works E5 and an Allez Pro made from E5 alloy. As jbhowat says, the frames are very different. The S-works is considerably lighter and the frame was built to a different spec. While the Allez Pro is a very good frame and one I use for crits it simply isn't in the same ballpark as the S-Works. People see E5 and think they are similar or the same - is all carbon the same? No.

Cipo won the worlds on the S-works and a host of other races. In todays marketed world of carbon the S-works E5 is a steal - an absolute steal of a frame.

Specialized ran a test where they made an S-works E5 with carbon stays - they gave it out to clubs to test. They dropped it. It added weight and wasn't as good as the pure racing frame.