What I have gathered is that quite alot of the pictures/faces that they have used are new, improved cutting and updated in genral. People made requests for players that were not on the FM10 pack have been added and things like that. The 3.1 update is just a few more pics 2000 more I believe added and updated, thats why you have to overwrite some of the files as they are new in technical terms.
Hope that helps.
cheers matey! but downloading them is a nightmare...i have spent the best part of four hours and i have only just got two so far..cuz half the time just when its about to download it tells u havent got an allocation or something daft like that...basically trying to get you to sign up!