Low/mid range cards won't benefit from having the extra RAM onboard I am led to believe, since they don't have the power to actually manipulate large textures and so on in high resolutions, where the extra memory would be needed. And the onboard memory is slow and cheap as well.
Those two cards would probably perform equally well. What is your friend hoping to play and what is his budget? You don't want to get him a card that isn't up to the task of Doom 3 if that's what he wants to play.