Well that's the key phrase right there. Obviously, a planet full of 8 billion humans consumes orders of magnitude more energy and resources than one AI, even with the robotic servants it might have. Which, by the way will be nothing like we imagine them, but probably something like the "grey goo" sci-fi writers have described, in other words a mass of millions of nano-robots that WILL probably be able to recycle and repurpose anything on a molecular level.

Long story short: if an artificial superintelligence becomes a reality we are woefully underequipped to understand how it will function. I can tell you that it will be unimaginably more efficient than our pathetic civilization that is profit-based (in other words it's based on a ridiculous game of Monopoly and not on the actual physical realities of our universe). It will make rockets and get all the resources it requires from space. Given enough time, it could conquer the galaxy if it needs to do so. I don't think anyone can say what it would decide to do.