Well, as some people has already suggested all benders in Avatar have some intelligence since they are human beings (except for a minority which are animals), so all benders will have a combination of both bending power and intelligence.
Anyway, a good comparison you can make to understand which one is more powerful intelligence or bending is to compare humanity with a really big meteor (which just as bending could be considered to be pure power without any intelligence). If a really big meteor would be headed for earth 100 years ago it would probably kill all humans, but if the meteor were headed for earth today then we might be able to stop it and if the meteor were headed for earth 200 years from now then we could probably easily stop it.
However, if a meteor were headed for earth 50 million years ago, then the crocodiles of earth would not be able to stop it and if it were headed for earth 40 million years later, the crocodiles of earth would still not be able to stop the meteor. So if you have a non progressive intelligence/very slowly progressing intelligence like crocodiles you wouldn't be able to become more powerful than things such as a big meteor/bending. Nevertheless we humans possess a progressive intelligence, which means that if we are given enough time we would probably be able to grow more powerful then any natural phenomenon. It would however most certainly take a huge amount of time before we could stop things like supernovas or even more powerful interstellar events.
An important thing to take note of is that, even though natural phenomenons can be extremely powerful there is still nothing except chance that controls these events so they can't really be used for something useful.
So to summarize my comment, progressive intelligence will eventually overcome raw power, and raw power alone is basically useless. So which is most powerful intelligence or bending, depends on the combination of bending and intelligence vs the intelligence of a none bender, so you can't really draw a general conclusion, since benders also (in most cases) are humans and therefore possess a progressive intelligence.