Koke is more defensively astute, a much harder worker, a better passer overall (other than through-balls), is a better dribbler, great at indirect set pieces, is much more tactically aware, and is 100% more consistent. To top it all off, he's done that against the biggest and toughest teams and then some. All at the age of 22. He's thrived and become a leader in Atletico under Simeone and whenever he plays with the NT (youth or senior) he fits in seamlessly into a technical game due to his movement and ability to click into passing tempo. He's played in every midfield position you could name and even as a RB once for Spain.
Cesc is a useful player because he can score and he can assist. However he does nothing contributory in buildup and his qualities always shine against the Mallorca's or the Rayo's of the world. His game is very limited overall and that's easy to see when he takes a shitter against 2/3 types of opposition and can't muster up any form in the 2nd half of the season (when we need our players to step up the most). A Barca team built with having Cesc as a starter would be very flawed and bite us in the ass in a lot of important games.
The VdB thing doesn't really make sense either as Cesc is about 5 years older than him.
But yeah, Koke's not coming either way. Atletico don't need to sell, Barca's not gonna make him one of the most expensive players in club history, and the amount of times he's said that he's staying at Atleti ranges around the double digits.