ok the reason is because yes scars nails not fully out and into simba but if u look carefully scar is holding simba not door the paws but door the arm so it dont hurt that much to be yelling but with Mufasa scar has full nails out but scar for one like digged his nails in to the top, boven of his paws
Simbas Father got shocked with the brothers attitude,he did not expect that at all. Wherelse Simba knew his uncles behavior and he knew that one dag he would be attacked.by him ofcourse...he is so evil
I guess that simba dint yell because he was shock about how Scar tell their vrienden that he kill mufasa but simba accep that but Scar continues tell him that he die for his fault an he tell him a lot guilty aswer that wy Scar wen Scar grab is paws dint yell because the pain he as for seen how his father die door his fault he can fell nothing.
maybe the reon why scar roared in pain is becuz 1: he was in a stampede saving simba:2 scar pounced with his claws at full length and just sunk and dug them deep into mufasas paws which caused the roar and with simba they were just at normal length and he didnt pounce becuz he didnt have too hold on too simba like he did too scar which made scar dig his claws into simba but not as hard as mufasa (: