Like with the jump from DirectX 9 to DirectX 10, you'll have to really concentrate hard to see what's changed between the two versions. If you can even really tell which version is which.
In that first shot with the swine flu guy, it seems the one on the right is a bit nicer looking, as in his head and mask don't look as polygonal as the one on the left. The two vents in his mask are actually round instead of octagonal, and there are more details all around. But that probably took you a while to spot.
I can't even see a huge difference in the second shot, where I reversed the DX10 and DX11 shots to make sure you were paying attention. Did you think the one on the right was better looking before I said anything? If so, you don't need to upgrade. More shots over at Firing Squad. [Firing Squad]