Having trouble deciding between two of my stories to write

So I want to write a publishable novel, and I have two well-developed outlines for two sci-fi stories. One is a YA solarpaunk, the other is an Adult first contact story. I've written a few chapters of both. I find the adult one easier to write and I think what I've written is better than the YA (rather rabbly and info-dumpy). The issue is that the adult one is something that I was thinking of being my masterpiece that I finish after publishing some other books so publishers will be more willing to pick it up. It's going to be a rather long collection of four novellas taking place over two-hundred years and has a bunch of metaphors and allusions. The YA, on paper is much more publishable. It's going to be an action-packed, fun story about a charismatic hero.

So how do I decide which to move forward with>