Force is Ultegra-level. Rival is about 105-level. There's a chunk of the difference right there.

I've ridden the Amira (entry-level; that's all they had in my size). Never ridden a Scott. They tend not to publicize what they're actually doing with the carbon. Specialized does do (if I remember correctly), size-specific layup, which is helpful if you're on the smaller side--otherwise you might end up on an over-built bike.