For me these stories were so incredibly similar that one of them seems pretty much redundant (though I'm not sure which one).
And *that's* the part that I find interesting. Not that you're obligated, but if you do any more cogitating on the subject and come up with something, please post if you are so inclined.
Mostly, the wording of that was a joke. If the stories are redundant, than they can only be redundant in combination, and so are both equally culpable for the redundancy.
Like I said, I think I like "Black Hill" just a fingernail-thickness better because it's explanation of the dead/ghostly matter building up in the oil seemed more convincing/eloquent than in The Sound of Gears.
Just 2 days ago, I posted a Best of Pseudopod 2011 list, and this story was on it as an honorable mention, but "The Sound of Gears" is not. As I was narrowing down the year's stories for the list, both this one and The Sound of Gears were on it til the very end. But I was aiming to make the list one entry shorter, and so the choice came down to eliminating one of these or the other because I felt they were pretty much the same--if someone reads the list looking for a good sampling of Pseudopod, I figured it would serve them better to not have basically the same story twice in this collection of 8. So I set the two on a metaphorical balance scale and measured very carefully to decide which one ended up on the list. If this story had not been published (or had not been published until after the year's end), then "The Sound of Gears" would've been on the list instead.