The E11, to me at least, is a substantially better amp when it comes to the quality of the sound compared to the E6. The sole reason I use the E6 vs the E11 when it comes to the clip is given the size of the two, they match fairly well. I'm sure someone can chime in as far as the effect on the battery, I don't have enough knowledge to give good advice on it.
Cool I'll keep it then. I just superglued a magnet to the back of my e6 so looking for something I can superglue to the back of the clip that's magnetic. I thought another magnet would do it but, I was wrong. Since I'm only using it at home for now size doesn't really matter.