I’ve said it before and I’ll say it again: The SG will not scratch with normal handling. When I say “normal” handling, I mean without throwing the phone around naked, bumping it to hard surfaces.
The silver band should be handled the same way but the main difference is that it will show “micro-scratches” after getting in contact with hard surfaces, putting a case on and off or by simply wiping it with micro-fibre cloth that is contaminated by sand or similar material hardness.
I’m not even recommending using polishing cloth that is wet because that may damage anything inside the holes on the band.
My SG X has been in and out of its case with no single sign of a micro-scratch...and this is observed under bright lighting.
A lot of people are getting the silver because they simply want change from their usual black/grey phones without realizing the silver band will scratch really easily (or are aware of this but don’t mind polishing every so often). One of my friends did the exact same thing and he is now having buyers remorse...worse yet, he is beyond the return period.
I don't think we really know how the Space Gray will hold up. It's a PVD coating on stainless, not anodized aluminum. The thread linked above is admittedly at the tougher-use end of the spectrum, but if people are careless with Lightning cables or keep other things in their pockets that an exposed part of the band rubs again, you could see some ugly wear. If you search watch forums, you'll find a lot of reports of PVD-coated watches showing quite noticeable wear.
How likely that is, I don't know. I have had a Jet Black iPhone 7 in an Apple leather case since launch and it shows no scratches you can see, at least none you can see without a magnifying glass, even in bright light. Properly done, both finishes (anodizing and PVD) can be very hard. We'll have to see what develops.