Nothing except an enhanced visual aesthetic and a tidy profit if you decide to sell it on. Korean steels with slips rise in value more quickly than anything else out there, which is why there's such a rush for them when pics appear.
The artwork on the Steelbook itself isn't much to begin with, nothing but a bunch of rectangles and headers. I'm glad I went with The Bourne Trilogy (debossed with actual art). I might get the The Bourne Legacy Fnac to complete the series.