AC can actually matter in this game so I normally look for items that provide AC.
In a game like Dark Souls where armour is less relevant because you just get obliterated unless you git gud anyway, I go pure fashion.
Of course, this is where systems like "Transmog" or other such appearance customization fits in, allowing the best of both worlds. You can run around in your BiS items making you super powerful... But you can also make them look cool and awesome too.
