If I write a document that I have to hand in to somebody (a report, summary, draft, whatever) I usually justify the text because it seems more appealing (at least to me) if it all finishes at the same length. However, now I read that it may be more difficult to read overall because lines do not seem so unique and the reader's eye may be misguided.

How do you usually hand in documents? Any advice or even scientific studies about that?