EuroGamer: "XCOM takes us into Unreal Engine 3 territory, meaning there's very little difference from a visual perspective between the console versions, though PC commands a few welcome graphical upgrades."
(PC, PS3, Xbox 360, XCOM: Enemy Unknown)
According to this article PC wins in terms of performance and graphics especially with more light sources than both console versions. 360 comes 2nd place suffering performance issues compared to the smoother frame rates of he PC. And PS3 comes out worst of the 3.
"but with gameplay this good, the PS3 version is still highly recommended."
80°
50°
70°
50°
Ad 
290°
30°
20°
20°
20°
20°
"but with gameplay this good, the PS3 version is still highly recommended."