VN10 makes a good point. De Ligt seems a generational talent in central defence.
Our last 2 decades of success has been built on generational talents in central defence (Puyol then Pique) Midfield (Xavi, Iniesta, possibly Busquets) Attack (Ronaldinho then Messi).
The question of debate is then, if we can only buy one of De Ligt or De Jong, which one is going to be a world class option for us for the next 10 years?
And secondly, for the one we do not get, what are the alternatives so that we do not rue not getting them?
I personally think its easier to find a great centreback than a great midfielder in the current market so would go for De Jong, while also admitting that De Ligt can be the bigger talent.
If we do not get De Ligt then there alot of options at levels similar to Marquez, Lenglet who as long as can play the ball well and excel positionally should assure our style.
If we do not get De Jong then unless we have an LE-esque manager who can bypass the midfield with vertically then we may struggle to find Barcelona level midfielders who are balanced.
Of course all this talk of generation talent and an injury can undoe it all. Umtiti was world class before his problems, and Kompany was probably the last talked about generational centreback before injuries stunted him.