Neither, since I can't seem to see what makes them so special. In the pictures, the two cities basically look like any other city would in a picture taken from above. I mean, have you seen how outrageously clean and modern Hanoi looks in these kind of shots? And it's actually funny that you have a picture of Central Park up there. I love New York to pieces, but ideal? :-/ And is that Utah I see? ::squints:: Private joke... 8-}
Seriously though, I'm not really sure what is meant by 'ideal city'. Is this just a hypothetical concept about a level of development that mankind has yet to reach? It is very difficult to imagine that we can ever come to a stage where we can safely say that all our problems have been resolved and there is no where left to go but up, because it seems that there is always room for improvement, not least in a city.
On the other hand, if the ideal city is one that already exists today (ideal in terms that it is superior to its comtemporaries?), I would think that cities like Singapore are pretty high on the list. However, it is interesting to note that most people when asked would not list any of these in their list of favorite cities (except if they lived there). Again, like me and New York. We are somehow drawn to imperfections and the challenges they pose, wouldn't you think?