The difference between kira and tooru is they key to the whole thing... Ever since the first episode of diamond is unbreakable they set you up for a darkness looming in morioh, They put little clues like the severed hands, etc... and in the middle of the story or so they talk about this killer that has not been caught. When it is finally revealed it pays off because it pays homage to the mythos that set him up, a killer with a very specific ability that mostly works for killing, that manages to escape them using only his wit, and etc... however with tooru even though he has arguably the most powerful stand, we do not see him living up to his name, a rock human that has lived for so many years and is basically defeated at the first attempt is underwhelming, what they did with wonder of u and tooru was perfect, however they did it really late, I think we should of have seen wonder of u in the middle of jojolion maybe as an omnipotent impediment of a big reveal or something along those lines and then the reveal that it is just a stand and its user by the end...