To change it, I'll have to go spelunking through either the HTML or the CSS, and if I was a designer, I'd probably pick the CSS. Looking for the 'product' class and tweaking a few properties sounds much nicer than figuring out how I need to change 'col-xs-4'. I'd rather have a conversation with the layout engine than struggle with some middle-man generic CSS framework like Bootstrap - it's simpler and more flexible (imo).