They did it for the torque. The speedy not only has a bit more, but it develops it at a lower RPM. thats where the difference is.....the lower max torque. Now the america has the same engine and therefore same specs as the 05 speedy instead of sharing the same specs with the pre 05 790 speedy.
Now looking at the specs you may see 4800 RPM's as the max torque. However, in 05 it showed 3500 RPM's for max torque. I don't know for why, but it would seem they decided to change the cam profile to add a bit of HP at the sacrifice of the lower torque to get it somewhere in between the old 790 and the 05 speedy. But looking at the HP specs they seem to be the same. So i don't get it. Why would the 05 SM have max at 3500 and the 06 at 4800 if theres no change in HP?
