Boy, that is such a difficult thing to do.
As I mentioned in my review, I have owned Sennheiser, Monster Beats and Shure (SE110, SE115 & SE215) IEMs. The Bang Olufsen A8 and Creative Aurvana Airs I wouldn't really class as in-ear as they actually sit in front of the ear canal.
These are the most expensive IEMs have paid to date, and to compare them properly I would need to listen to an expensive or high grade IEM. However, what I can say is they are the best IEM I have ever experienced, far bettering anything else I have used previously.
I also own many on / over ear headphones (AKG K550, B&W P3 & P5 and Sennheiser Momentum's) and I must say that I am finding it extremely difficult NOT to listen to the KEFs.
I am surprised I cannot find any other reviews across the Internet so perhaps this is a worldwide exclusive.
The only thing I can say is if you really love your music then get these.