Has any Xbox users played both Xbox versions and PS users played both PS versions of FC4? I can't say about the PS versions because I haven't played them on there yet. I noticed two differences with the Xbox versions. In the Xbox One version there's more people in the Golden Path and they are older than the others. The other difference is the man carrying the basket. There's only two versions of him in the Xbox 360 version and three versions of him in the Xbox One version. In the Xbox One version the third version of him shows him with a beard. I find it interesting why different platforms to video games are slightly different. Rockstar have done the same with GTA III, GTA: VC and GTA: SA
Every object in game (human, tree, car or what ever) needs its 3D model and textures to be loaded into the computers (console or PC) memory. As newer generation consoles and PCs have a lot more memory available than the older generation did, it is possible to display a wider variety of objects.
Also there often are different groups of developers (or even totally different companies) making the different versions of the game.