Other than providing a nice interface what does Charles.app do that something like Burp can't?
Charles is not new, it's been around more than 10 years.
I think that generally saying 'what does X do that Y doesn't' comes across as fairly negative, and unless there's some obvious reason why Y should be the default adds little.
I'd never heard of burp, but I had heard of Charles. Is there some obvious reason why burp should be the default?
edit: additionally, Burp uses a custom certificate instead of a default one for all Charles users
Nice article by the way, when attempting to extract data from a site looking at their mobile app is the best thing to do :)