Since there is no measurable performance advantage for either, any time (however marginal) spent thinking or talking about a choice between the two is wasted. When you prefer single quoted strings, you have to think when you need interpolation. When you use double quoted strings, you never have to think. (I'd also add, anecdotally, that apostrophes are more prevalent in strings than double quotes, which again means less thinking when using double-quoted strings.) Therefore always using double-quoted strings results in the least possible wasted time and effort.