I personally prefer brackets as my 'developer' eye is more trained for it. For end users? Shouldn't they be using child themes anyway? Also, I wouldn't trust ANY client editing theme files with PHP in them. If they can't style it with CSS then it's outside the realm of "EDITING" the website.
What would they need in a theme file for? Adding an author field to the theme? What end user would know or want to mess with that.
Again, an example, they wanted to make a custom page in a way that requires them to make a new template file, like a mortgage calculator, then they should know PHP or what they are doing anyway.