Seen at a glance, the difference between the two is very visible, especially when Barcelona was still under the command of Koeman. But since Xavi took over from Koeman Barcelona slowly improved. And their last meeting in a match titled El Clasico Barcelona was able to beat Real Madrid. Indeed, it can't be said that Barcelona fully equals Real Madrid, but with that result I see Barcelona making progress in that direction.
Xavi is a product of the original La Masia academy, so he has Barcelona DNA. He knew what the fans wanted, but he knew it would take a lot of time. Barcelona managed to improve their form after Xavi took over from Koeman, so this is good evidence that Xavi and his strategy are very useful for Barcelona.
I think his first season as Barcelona coach went well, it wasn't perfect but ending the season in second place after slumping in mid-table is something to appreciate. I will see how Xavi is able to restore Barcelona's glory, maybe next season they will be better.