1. Better visualization than XBMC
2.DTS HD MA support which XBMC does not support.
3.Support for ISO file. XBMC does not support ISO.
4.Bluray Disc and DVD Disc support XBMC does not support Bluray and DVD Disc.
5.Third Party Player support. You can use any player with Media Browser (Klite codec,Power DVD, TMT etc..)
6.Better Movie management.
7.Better theme (see Pearl screen shot).
8.Better plugin support.
9.And etc etc. Please install Media Browser with Perl theme,Cover art3,IBN People Provider and Mediainfo Provider plugin then compare it with XBMC you can clearly see the difference.
I have 200 DVD ISO and 20 Bluray ISO in my collection.If you don't have any ISO and play only small MKV file then XBMC is fine for you.