I'm at a Fork in the Road

So, I've been talking about writing a story. In it, a guy obsessed with World war I aviation is tasked by Celestia to start an actual aviation unit. It takes place between Canterlot and Ponyville, and has eight little arcs planned.

Then I came up with a different idea.

In this one, a British pilot from 1915 finds himself near Stalliongrad, a northern country mostly independent from Equestria. Not only will he need to tend with creatures he's never seen before, but a problematic government. I only have three or four arcs left, but I believe it should be quicker to work on.

So, which should I work on?