I would vote IV. In my opinion IV is a far superior game with its addons to V. V feels like it has been dumbed down somewhat, of course thats only 1 persons opinion, but I have many fond memories of late night games with my mates on IV, where as V was just not as good. Graphically its beautiful, but a certain crispness seems to bemissing in the game play unless it has been patched up recently to change anything ?