I think you're getting a little confused, the entire Allez line uses E5 tubing with the exception of the Sport which I believe is steel. Also, you also seem to be confused with the order, best to not best is the following:
S-Works
Pro
Expert
Comp
Elite

Besides from a little weight and the components there is not much difference between the S-works, Pro, Expert, and Comp, they are all basically the same frame, perhaps a slight difference in weight but that's all. The S-Works and Pro are VERY similar in components as well. If the S-Works and the Pro are the same price obviously get the S-works just for the name itself but I wouldn't spend too much more on it. As I said, basically you're just paying for components and the name, I mean everyone knows what a S-works is. I do love the Allez and E5 S-works framesets though, they are extremely stiff, enough to knock your teath out, that said they are GREAT for climbing and sprinting, I have a '04 S-Works and I absolutely love it, my butt gets a bit sore on longer rides since I feel every bump on the road but it's totally worth it. The tarmac and robaix bikes tend to be a little more subtle in the feel of the ride than the E5.