The difference you have shown is the difference between the "traditional" frame and the new "compact" frame. The compact frame has a smaller frame hence the sloping top tube. The idea is that a smaller frame is lighter. But the problem is that you need a much longer and stiffer seat post. Any weight savings are apparantly lost when you add in the seat post. So it seems that the compact frames are an improvement that isn't. However, if you like the looks of the compact frames, by all reports, they are perfectly good bikes.