Of course there is a performance difference... you pointed it out yourself: "single quote also does not parse escape sequences such as \n and \r." -- since single quotes don't allow the parsing of \n or of variable names, it can be treated as literal text and doesn't need to be run through any further processing. I work from the opposite opinion... I use single quotes, unless I'm inserting $vars right into my text. And even then I'm not above .concatenating.my.strings.together either.

-tg