Ryder, you are indeed correct. Racing pads such as Ferodo DS2500s are not fully effective until you warm them up a bit, whereas road pads such as Ferodo DS are good from cold, but not quite as fade-resistant at the top end of the temperature.
With regard to discs, there are various factors to consider with regard to the surface. Some are drilled or grooved, which improves cooling when really going for it, but reduces pad contact area, and increases pad wear (plus some maintenance issues). So let us assume we are talking OEM blanks versus something like EBC blanks. Metal is metal, with a similar friction coefficient so the real difference is the quality and tolerences. In terms of braking performance, they will feel the same, but it is on the ragged edge that the higher quality discs should resist warping and other deformation.
As for the pads, friction coefficients can vary hugely, as well as temperature resistance. A good pad should provide solid stopping power when cold, and minimal outgassing when hot to prevent fade. In this instance, an aftermaket pad is likely to improve braking performance.
