Well if you must have a border, the middle looks the best.
But if you want my opinion, here’s what I’d try.
I’d play with the sizes of things a bit. You’ve got a lot of small scattered images at the same size and visual presence that there is lacking perspective and grandness of objects of space.
I would scale up the earth and fill the top header area of your cab , but not obscuring the spherical shape of the planet. So leave some small black space in the front of that top part.
The astronauts are all at wacky sizes and so evenly spaced from one another. It’s hard to tell who’s in front. I’d make a couple guys bigger, so the seem closer to the camera in perspective, and I’d also overlap a couple in some areas.
I’d remove one of them too. Probably the one that’s duped and flipped. While you’re at it, raise the ship a bit and make it larger as well.
Remove the image of the asteroid at the kickplate, that’s just creating an anchor in your composition because it’s a small detail that has no reason to be there, and is attached to the frame edge. I’d get rid of the planet by the front CP area as well.
These are unnecessary and I know that you’re just trying to fill spaces here, but less is more. The planet in the middle near the monitor edge doesn’t need to be too close to center of that area. Offsetting it to the back edge more created a nicer non-symmetrical framing of it. If it’s too symmetrical it becomes boring and uninteresting to look at.
Also, I’d flip the black hole so that it’s angle isn’t in parallel with the ship’s and earth’s directional lines they’re pointed in. The black hole should be facing the front of the cab.
And the ships battling should be much bigger so you can see them clearer ,and I’d have one of them overlap the black hole’s outer edge a bit.
Try these things and see if that helps.