Compares text files well, but has limits. – iDiff View Review

It's a straightforward text file comparison tool. The files you want to compare have to be on Google Drive, iCloud, or some other cloud service that supports the Document Picker Open method. The comparison seems accurate and easy to read. Minus one star for not being able to send files to the app directly, nor indeed to paste text in. Minus another star for not being able to do any editing. All you can really do is look at your results. If you want to implement changes, you'll need to switch back and forth between this and your editing app.
Review by Drag0nSilver on iDiff View.