I'm not sure. I would say Tobi since he could warp himself inside Susanoo right behind Itachi and if he has Rinnegan, use Human Path. If he doesn't, then I can't think of any other way other than warping Itachi himself into his pocket dimension.
I guess Itachi could catch him under genjutsu but I don't really know how skilled Tobi is in genjutsu so I don't know whether he could break out of genjutsu at Itachi's caliber or not. Itachi's only chance here would be Genjutsu, if it works, or Tsukyomi, if Tobi happens to look into Itachi's eyes before he warps behind him.