I have both the Ti and sport versions. The Ti has a carbon fibre shell while the sport is plastic. I don't have a scale but it seems the sport is a little heavier. The sport has manganese rails and I think the cover is not as soft as that on the Ti version. It could be that my Ti saddle is broken in while the sport is not. Both have the same shape.

But, somehow the sport just doesn't feel the same to my butt. I thought it needed some break-in time but I replaced it with another Ti version and it felt fine right out of the box. In fact, I did a century on it the second ride and it was great. So perhaps it is the rails, the cover, shell or padding that makes the difference for me. If I hadn't used the Ti version I probably would have tried to break-in the sport some more. Maybe it's all in my mind.