Kinda what Rayraz said, kinda what Quest, Bobby, & Grafikeer said...  I like image 1, over-all, but really have very little issue with either.

I think in the lighter one, the backside of the small moon is too light... Even if the planet we're standing on has a wicked high albedo, my brain doesn't want to see the "dark" side of this moon being so bright.  (Or, is that the planet, and we're on the moon?  Either way, I think washing out the 'moon' detracts too much from the beautiful surface detail you've put into it.

Were it me, I'd break up the image as far as applying different post work to different elements:  I like the dark side of the figure and the moon dark, so I'd mask and leave them as is in #1...  I'd probably black up the space elements even more and pop some elements of the nebula and stars, with contrast or dodge & burn or both (with the caveat that, admittedly, I usually contrast the heck out of my nebula images anyway... More like NASA false-color photos than actual photography.  I just like the really bright nebular elements.) 

I'd preserve the detail in the surface area behind the figure as in #2, also, and (after playing with it a bit) maybe even amp up some of the highlights on the suit. 

I guess the short version of all that is I'd keep most of the darker one, make some selected areas even a little darker, amp up contrast more.  Some of that might reflect that I'm on a laptop in a dimly lit room (rather than utter darkness, which I prefer) but, in general, I prefer space images to be more dark and contrasty... No atmosphere to dim and gray stuff out, perhaps.