I don't actually have a ruler built into my eyes, but I think the Xbox360 looks to be a bit taller and wider (bottom and top) than the PS2.
After a longer look at it though, it also seems the controller is placed lower than the console itself which might add to the overal impression of the size. The drive might be a good indication thoiugh to make some good estimates.
Having said that and ignoring size: I really don't like the shape of this thing, neither the colour nor the black lines (drive, iR). I'm not sure when things went that white apart from Mac's but all my equipment is either silver or gold finish - not white. Not a very good start if you want to be in the center of the livingroom IMO. I edon't like it much, but maybe it's just an awkward picture.. :?