Ho-oh. Lugia's the most overrated thing since the invention of sliced bread, and even without that it's one of the most effortlessly designed legendaries I've seen. If nothing else, they put a good amount of effort into the head but very little into the rest of its body. It looks hilariously out of place among the other legendary birds(Pokespecial was the most striking example of this, but if I shared pictures then I'd go onto the mod team's hitlist), especially due to those hideous wings. Change those to something remotely decent(bat wings, dragon wings, bird wings, ANYTHING) and Lugia tends to look drastically better.
Ho-oh, on the other hand, is just plain beautiful. A phoenix is less creative than a...dragon seagull thing..., but it certainly came out looking better in the end.
Battle-wise, Lugia is tops however much you like or hate it.