This discussion was extremely helpful to me in deciding to get DHP (VDC). I don't have the car yet, but based on this feedback and review comments, it seemed like the best option to get. I've driven both DHP and non-DHP X3s and the DHP car feels more lively and connected.
http://x3.xbimmers.com/forums/showthread.php?t=698812
Also, this topic has been widely discussed on this board. A quick search will produce ample results. Good luck!