Lugia, in my opinion. First off, yeah, better speed and defenses, although I admit that Ho-oh has better offensive stats (...with less speed). Second, okay, so Lugia doesn't have the attack power or the 50% chance to burn the opponent (which probably really wouldn't matter all that much anyway, considering Ho-oh's offensive stats... or midland defenses), but it is a fairly impressive wall, which has already been touched upon already. Third, as also touched upon already, Ho-oh's got a 4x weakness to Rock-type moves. So, either way, it's "lol, Rock Slide/Stone Edge."
And to complete the package and respond to DarkArcz, Lugia has Pressure too. ^_-