You are comparing two different players but overalll Pjanic is definitely better
Kovacic is a great talent and you could see it right away when he played for Inter
Real bought him and I thought it was a great piece of business but I was also surprised as Real didnt buy too many Serie A youngsters back then..
Real turned him into a very good player - NOT WC YET...
He is agile he defends way better than Pjanic (who his defensive aspect really lacks IMO)
Pjanic is an organizer Kovacic is a B2B so its not easy to compare them (and not right to do it anyway)
To say Kovacic would take a team and give them a real boost in quality - Nope (He will improve them but he wont be a real difference maker)
As I see it Kovacic is a great player who can become WC but has yet to get there
Pjanic is definitely WC as what he does not many can do
Pjanic`s role is also more unique - There arent many great players in his role - The only ones I can think of are Verratti who rotates the field and the treatment table, Modric who is the goat of the organizers and please forgive me if I forget a player or two but the thing is there arent many
Its way easier to find a good B2B..