There is nothing more encouraging than to be a writer and have not one, but two inspirations! All of a sudden you have two ideas, two plots, and two amazing worlds to create. The problem? Well, you can only handle one story at a time. Some people try to jump back and forth, writing two stories at a time, but it doesn’t work. You have to choose one story that you want to turn into a novel. It involves listening to that little voice inside your head, telling you what story to write. And remember, it doesn’t mean you’re abandoning the second novel, you’re just saving it for later.
I suppose you would need to choose the one where you see more passion and attachment. These aspects would allow higher creativity and focus. It might even allow you to explore possibilities of cross fertilisation of ideas.
Shakti