Chris, I don't see the point of that study, other than to try and frighten parents away from the word 'academy', or to otherwise push an anti-academy agenda. It would have been much better if it had looked at the outcomes for individual schools to see whether they had improved since becoming academies. Many of them will have become academies because they were failing when they were council-run. If they are improving from that position then that is good, if not then there is a problem with that particular academy provider. If a large number of them are not improving then there is a problem more generally with the programme. However, the Observer article doesn't allow us to make that judgement - it just compares academies with other local schools that presumably weren't failing in the first place.
Schools thrive when they're well run. They can be well run by councils, and (we expect) they can be well run as academies. Taking our three academies as examples, they were doing very badly when they weren't academies. Now that they are academies they are improving. That might be because they're being run by a third party, or it could be that lots of concentrated effort and money is going into improving them. From a purely practical point of view, if they hadn't become academies then that money wouldn't have been made available to them. A lot of this academy/free school legislation has come about because the government don't trust local politicians to turn around failing schools.
One practical advantage I can see in the case of our academies is that the academy sponsors will not care which borough their children come from. Unlike councils, their duty of care does not stop at the borough boundary.