Even though Ho-Oh has a more powerful attack, the 4X weakness to Rock Types makes me lean more towards Lugia. Of course I think Lugia looks cooler than Ho-Oh, but I'm also more of a "defense prone" player. So if I were to have one of them in my team then I would of course pick the more defense prone Pokemon. Aeroblast's high critical hit ratio also makes me lean more to Lugia, even though it's not the best move ever, since Lugia is more defence prone it's going to need some pretty powerful attacks like "Aeroblast". So I would have to say my vote is to Lugia.
EDIT!: Lugia does also have a weakness to rocks, I know. But it's not as bad as Ho-Oh's
IMO!