I'm not brand loyal, but I won't purchase unknowns - I've done many a track day where certain model of tyres do not perform, when similar from other brands are fine (and this is something that changes with time). Some of the issues were premature failure, some of them were dangerous handling traits.
Also when you look at model/brand specific communities you often find there are certain sets of tyres that perform well with certain cars and some tyres that are known to not perform well with certain cars. So when I've observed a certain car having issues with its tyres on a track, I've not assumed those same tyres will be bad on my car, but I use as a point of reference to research if there is a general issue with those tyres of just specific to that car (or car setup).