How Does Septal/Rib Cartilage Feel Post-op?

Depends on level of structural support. Most of the time, if extensive structural grafts are used, your tip will feel stiff.
 

Your nose is typically "stiff" following rhinoplasty but this will lessen over time. The reason for this is that cartilage (septum, ear or rib) is typically added to replace missing structure or reshape the nose. This will result in a "firm" feeling of the nose that will decline over time. Further, if an external rhinoplasty is performed, the nasal tip skin will be numb for three to six months and this can further make the nose feel "stiff."
Best,Stephen Weber MD, FACS

Depending upon how either one was used will determine how it feels. If the rib cartilage was left very thick, then it would feel firm. If the rib cartilage was thinned like septal cartilage it may feel more flexible.

Septal cartilage is much thinner and tends to be less stiff than rib cartilage.  Rib cartilage is typically used to augment the nasal dorsum when there is insufficient septal and/or ear cartilage available.  Septal and/or ear cartilage is typically reserved for the nasal tip first (due to its pliability).

After rhinoplasty the nasal tip is routinely stiff, this is because we use cartilage to support the tip to keep it from dropping as we age.  Both septal and rib cartilage will make the nose stiff, that stiffness does lessen somewhat with time.