I have done both styles in the past and find that I have to do a combination. During rehearsals, when I have to take down blocking more than anything else, I'll put the text on the left, stage diagram on the right. I then write out a separate cue sheet with cue #, actor action or key line, and time of cue. Then when it comes time for tech, I can read off the sheet as I go through the script and really finalize my timing, which makes it a lot easier to time my "ready"'s. I have even been known to retype scripts with color-coded cues in the left margin (still on the left side of the prompt script) which leaves my right side free to jot notes during the show. (Yes, I'm a tad OCD) I'm all about the left side now. It just makes me happy.