In Canada, the aluminum watches start at $519, while the SS ones start at $929. Since I don't need cellular (which would add $130 to the aluminum cost and make the difference in price smaller between that and the SS), it's extremely difficult for me to justify paying double for SS.
My Apple watch history:
I had an Aluminum 38mm Series 0 for a couple of years, then got a great deal on a used SS Series 2. The SS absolutely looks nicer and matches my bands better (since the Milanese and Link Bracelet have SS lugs) but I actually found it worse functionally because the vibration from the notifications wasn't as strong due to the SS being so much heavier.
With the watch still being in what I consider "early days," I'm probably going to drop back down to aluminum this time around and maybe jump back up to SS in a few years when the upgrade cycles are longer and I can justify the huge premium.
As far as "scratch resistance" goes, the glass on my aluminum Series 0 never got scratched and I wasn't exactly delicate with it. I haven't noticed a difference between it and the sapphire screen on my Series 2.