I'll be in the Rhineland next week visiting Düsseldorf and Cologne.
The two cities are about thirty miles apart and have a sharp rivalry going back hundreds of years. Coming from Manchester, I know about rivalries with cities thirty miles downstream but whereas the competition between Manchester and Liverpool centres on football and music, the Rheinland one is expressed most clearly over beer: Alt in Düsseldorf and Kölsch in Cologne.
Maybe this is because Fortuna Düsseldorf are a bit like Manchester City, bouncing up and down the divisions not winning anything, and neither city as far as I know has been the centre of a music scene like Merseybeat or Madchester, but I still can't think of any other two cities so close together which denigrate the beer produced in the other. I've not been to the Czech Republic but I don't think the competition between Pilsen and Prague beer extends to calling the other one undrinkable.
For the record, I like them both (heretical in the Rhineland), but if I had to pick one it would be Alt.