wow. that's a load of shite of the highest order.
absolutely no manager would take jones over cahill. get a grip.
It's not shite at all. Have you noticed that people have only started to rate Cahill since Mourinho came? Why? Because Chelsea's back line now that have the best protection in the league and the responsibilities placed on the CBs is completely limited. When they aren't protected or have to come out at teams, they are all over the place - look at Tottenham, look at Atletico Madrid, look at all the points they dropped last year vs weaker opposition.
Jones is a defender is much better. He's better at getting tight and at sweeping, he's faster, he's better in 1v1 situations and he reads the game better. Cahills strengths are that he's good in the air and he's brave, which is why he suits Chelsea system because he does most of his defending inside his own box, but he's severely limited.
Jones makes sloppy mistakes, I'm not disputing that. He's 22 years old though and they are the mistakes of an inexperienced centre half. Cahill is 29, and actually makes just as many mistakes but it's because he's an average defender, you'd be mad not to swap him for Jones. Could Cahill play on the side of a 3 at the back? No. Could he play a high line? No. He's limited, and one thing that people do underrate massively is Jones' positioning in an around the box; it's impeccable, especially on balls whipped in. He is more than capable of doing what Cahill does week in week out, that's not the case vice versa.