“Who cares? Let’s just go with the style-guide” — to which my response is that caring about the details is in the heart of much of our doings. Yes, this is not a major issue; def self.method is not even a code smell. Actually, that whole debate is on the verge of being incidental. Yet the learning process and the gained knowledge involved in understanding each choice is alone worth the discussion. Furthermore, I believe that the class << self notation echoes a better, more stable understanding of Ruby and Object Orientation in Ruby. Lastly, remember that style-guides may change or be altered (carefully, though!).