"Stiffness" in a bike is difficult to quantify, and its benefit, or lack thereof, varies depending on the rider and where you ride. Heavy riders benefit most from a very stiff bike. Light riders suffer on stiff bikes, particularly on rough surfaces. At 145#, I find stiff bikes difficult to control on rough pavement.
So, don't take "stiffness" as the single arbiter of a good bike. Ride what works best for you, and let the marketing department worry about "stiffness."