• The representation of internal organs in DOOM 3 (eg on corpses or zombies) was removed
• All multiplayer modes in DOOM & DOOM II have been completely removed in the PS3 version! (no joke)
I can confirm these changes because I even imported the Japanese version and this learn "the hard way" had to me. In particular the absence of all the multiplayer modes in DOOM & DOOM II is a big disappointment for me.
Unless you plan to take up the Japanese version only from collectors reasons on the shelf, it is better to make a wide berth, preferring to grab PEGI or from me also to the German USK version.
And, although the publisher in advance always, there was talk that there was only a single, worldwide identical version.