I've had this conversation with so many people over the years and more recently with students. The biggest contention always seems to be shoes! A gentleman in jeans, with a t-shirt, jacket/blazer or smart shirt or shirt and jumper, can rock it both ways. Throw in a pair of trainer types shoes, and it throws the balance'! Ladies, just tricky if not more! Peep-show shoes? Sandles? Converse? Espadrilles, Flipflops so many factors to consider but shoes will kill or make the outfit, smart, casual, street whatever!!