Durham v Warwick Maths

When people are ranking unis for Maths from what I’ve seen there is normally a top 4 of Oxbridge, Imperial and Warwick followed by a second group of others such as Durham, Bath, Bristol, UCL all on about the same level but what is the difference between somewhere like Warwick v Durham for maths and how big a difference actually is it? Or Bristol v Bath v Durham for example. There always seems to be debates over how big their differences and quality actually are for Maths courses, especially when it seems the entry requirements/reputation is not that varied for most of them.

Thought it was interesting to discuss, any thoughts welcome.