The design and materials of a brake make an enormous difference in stopping power, fading, and linear or progressive pull for power. Brake flex is an enormous power sucker, but perceived and real power also comes from lever flex, cables, cable routing, springs, the rim they are on, seat stay rigidity, etc. The same pair of brakes on a different bike can act differently. You are correct that often a design can remain the same, with step ups like bearings instead of bushings, and forged parts. However there will be a big flex and power difference between a die-cast brake and a cold forged one.

Many low end brakes do indeed stop just fine. Really just fine. Until, one day when you try a pair of Dura-Ace or Mavic SSC you realize, wow, those brakes not not fine, they are incredible.

His CAAD9 5 did not come with Campagnolo, and therefore Campy brakes without a release lever are not practical. Same goes for one of the best brakesets, the Mavic SSC. Yes, some people do it and squeeze the tire through, but why bother.

The bike came with 105, so look to new or used 105/Ultegra or Rival if you don't mind mixing for a cost effective and acceptable braking alternative to the Tektro. But yes, different pads may do it or your current pads are just glazed badly.