It has nothing to do with the brand. It depends what kind of crystal is used. Most likely if your Citizen is really scratched up, it's probably using an acrylic crystal. On lower end Seiko watches, they tend to use Hardlex (Seiko's version of mineral glass) which is much more durable and resistant to scratching. The toughest crystal would be sapphire which is used on most mid-tier and high end watches.