A few theories as to why they changed it:- People were getting tired of hearing the same song every week. (I know I was.)
- The song has been topping the chart, I believe due to its use on Idol. I'm sure it's selling a lot of copies on iTunes and the like. Two versions? More sales!
- What Frisky said, about the particularly "sad boots." Elliott got the slower, mournful "Bad Day" too.