That's actually a good point, every pastelaria that I am aware of sells only Sagres and Superbock and they are the vast majority of bars. On the street where we live there are five or six or them and no other bars.
There is a bit of a rivalry in that Superbock is from Porto and I've been told that often people refuse to serve you Sagres if you ask for it there. I dunno if that's true cos I've only been there once, but I have heard it several times. It's one of those rivalries that's a bit pathetic cos it's unreciprocated.... you know those things where, I dunno.... England hate Germany at football and think that every meeting is the grudge match of the century but Germany barely notices that England exists, treats it as any other game and almost invariably dicks on us anyhow.... except not this time eh, stick that up yer arse you... er, sorry where was I?