Byword vs Disk Inventory X

In addition to plaintext, Byword can export to HTML, PDF, RTF.

Byword de-emphasizes the syntax itself, while emphasizing its effects. It appropriately adds style, like italic and bold, to text that's designated by markdown and dims the syntax so it does not getting in the way of comprehension. Additionally, there are commonly used hotkeys (⌘b, ⌘i, etc) that can be used to apply style without having to know the syntax or having to type it out each time.

For example, while authoring a bulleted list hitting return automatically prepares a new bulleted line.

Byword is available on a Mac, an iPhone and an iPad.

Documents can be synced using iCloud or Dropbox from within the editor for use across all devices.

It is absolutely free and released under the GPL.

This way you can find what is taking most of the space.