PPE at Durham is on par with other non-Oxford universities offering the course.
To be honest, the course content in any of the top 10 universities for PPE is unlikely to be radically different. There are however, subtle differences in the delivery methods, assessment and wider support available for students.
Naturally, Oxford has the most renowned and arguably most effective delivery system with personalised tutorials with the leading academics in the field (alongside lectures of course) - everywhere else it's all pretty much the same - lectures + seminars with pretty damn good, although perhaps less renowned staff.
Assessment at Oxford however, is different to everywhere else as all of their summative exams happen at the end of their final year. At Durham, we study 6 modules per year - the exams for which we have at the end of each academic year. Other universities, such as Warwick and York, have a more 'continuous' assessment with exams at the end of each term. This allows them to have arguably more flexible programmes - with more, smaller modules being studied during any given year, but of course, that means more exams.
As for the more ambiguous category of 'support', Durham and York have established extensive societies that seek to reinforce the course on academic and social grounds that make them stand out from other PPE courses in the land. Or at least that's what we like to think.
Anyway, the point is, at good universities the differences in what you learn and how you learn it will be minimal. What will differ greatly will be the overall atmosphere of the place so it's best to visit as many institutions as possible to find out where you fit in.