I was in this same predicament as you:
I have the First Generation Watch, and I got rid of it for a few reasons. I got a great deal on that Watch too when I got it a year ago.
The Space Gray sport model I had was just fine. I don't use it for too much outside of activity tracking and notifications, only which calls/text are most important.
The upgraded look/feel appealed to me, the water resistance, and the faster processor. (Not to mention the small speck of dust on the screen.) I wanted something that looked good and functioned well.
I originally went back to the Sport, and Nike version at that causes that the only way I'd go Sport. It was a bit more sporty than I wanted and also the actual Watch felt like my previous one like I didn't even upgrade.
So I dug in and really upgraded. Got the color I wanted with the band. I miss the old one a bit as it served my needs just fine but the Stainless black which I consider Low manitence has the features and the look I wanted.