I've gone with Space Black Stainless Steel ever since Series 0, and upgraded every version in the same finish. I always kept my Stainless Steel Link bracelet, I love the combo.
Series 5 I wanted to change it up, and ordered the Space Black Titanium. It is built extremely well, but the shade of color ended up being lighter than I was hoping when put on the Link. I ended up selling that and this weekend purchased the Space Black Stainless Steel. You really cannot go wrong with the finish, and I am loving the California face with the always on. Now I can't wait for the Watch OS update that is needed badly! Everything about this watch is great except for the battery life and the very slight delay on waking up from almost on. They fix those 2 issues, and this will be the best version of the Apple Watch they have put out!