Historically, first came the symbols, then the abbreviations. Early men carved the first symbols on the cave walls while abbreviations are only as old as the Romans. Which of both is understood better, depends on the context. Symbols have already proven their indispensability in the digital...

At Squirro, we jumped on the Google's Material design bandwagon quite early on. Arguably, a wise decision as it allowed our design team to focus on the user experience instead of general discussions around guidelines.