When you say HU do you mean "Head Unit" i.e. the central LCD display, or "Heads Up" as in the flip screen above the dials?
If you are talking central display, I also have the smaller 6.5" screen with extened bluetooth and the basic navigation (not the XL pack).
The differences that I can tell are (the XL has over the non XL
1. Handwriting recognition
2. Ability to play movie files
3. Split screen (map on one side, music list on the other)
4. Larger LCD (8.8" vs 6.5")
5. Connected XL (whch has more features)
I don't think there are any other advantages
I did not know that when you buy Chili, the Media XL drops by about £500. Had I known this I would have gone for it, as that price drop makes Media XL only about £200 more than extended BT+basic Nav.
However, 6.5" is big enough for me, who needs those extra 2.3!