I had thought about it hard when the first version of the watch came out. I ended up getting the Space Black. I also have the Space Black Link bracelet for day to day. I have a Leather loop, and a Nike black Sport Loop when I want to change things up a bit. I have a Nike rubber strap black on black for workouts and swimming.
The thing that pushed me over on the Space Black was the incredibly polished finish. It is a shiny ink black that you dont know where the case ends and the screen begins. It is sleek, and stealth. With the Link Bracelet, it just goes together so well. The DLC finish is so durable, to me it looks like it comes right out of a Sci Fi movie. I wear it with pretty much everything except when I am dressed up going out, then I will typically wear one of my Mechanicals. I swayed off the SS primarily due to scratches. SS will tend to mark easier. I have had every version of Apple Watch in Space Black, and I hope they will always make them. The Aluminum I am not a fan of primarily due to preference of Steel and Sapphire.
Just wanted to chime back in that I ended up with the Space Black Series 4. It really is a unique finish and looks extremely cool. What strap are you wearing on your Space Black at the moment?
I have mine paired with Apple's Black Woven Nylon strap and am happy with how it goes with the watch.