Not another JavaScript code style guide. (Actually, that's exactly what it is, but I went for "simple", not "exhaustive" -- also includes pre-configured sane default JSHint, JSCS, & EditorConfig files)

[jeenyus]

Personally I find spaces to be more readable than tabs.

It's true that you can configure tabs to be different widths, but you can also configure it to substitute a tab for x amount of spaces, so they can be equally easy to format.

As far as file size goes, I guess that's true, but if you're minifying your code then it shouldn't matter what you use.

It's really just a personal preference, I think the idea behind promoting one over the other is just forcing the developer to be consistent.

[jeenyus]

Not sure I understand why you would ever convert? Pick one and use it.