NO2, IMO, is a waste of money, many people say it doesnt work. but creatine on the other hand, the only thing that's debatable is how well it works. i'd go with creatine, cheaper and more effective.
I think NO2 is more a mind thing... I loved how much it ballooned my muscles during the pump phase. It may not have done anything other than that, but it was more than enough to motivate me to work harder!
I agree with MReik about Creatine working physically.
It is up to you... I you dig the pump and like the blown out muscles, NO2 may work nicely for you.
Why not try each of them for 3 months with a 2 week break in-between? You have the rest of your life to do this!
along with the fact that creatine is proven to work in most people, while the same has not been conclusively proven for NO2...NO2 is hella expensive. waste of money and time.