I just exchanged my SS iPhone X yesterday for a Space Gray variant.
I had the SS one since launch day and it went from the box to an apple silicone case. The only exposed part was the bottom where apple feels it's a good idea to keep open...lol
Either way I used my phone as I normally would, was pretty carful plughing the lightning cable in until I picked up my wirelsss charger, and it went in and out of my pockets the whole week, granted I'm always in sweats or sports shorts or pants, rarely ever wear jeans so this phone didn't see the inside of jeans, just every day use for the last week and I saw no visible scratches at all. I took it out of the case a few times to just check it out and I noticed 2 very very small hairline snips one both sides, that most likely only a maniac like myself would really notice anyway. But to my surprise nothing on the bottom by the speaker or lightening port. All in all I'm pretty carful with all my phones!
To own the silver model you will need to put some extra tlc in if you want to keep it pristine, and if you're using an apple branded case there's a little more to it because of the exposure at the bottom, but going full caseless is just asking for scratches and I'm just not on board with using a cape cod cloth on this phone. I chimed in on a few threads as to why, and people are just in denial. That stuff gets in your speaker grill, or on your screen...lol the party ends right there and you will have a bigger headache than you started with..just my 2 cents for the silver.
For the space gray, well I just love the whole stealth look. Again it went from the belkin machine where a glass screen went on into a brand new midnight blue silicone case...And that's were it will call home...lol, unless I'm switching case colors or into an apple leather case. I love the bottom how it's all black. And yes if you jam a lightning cable in and out you will probably scratch it somehow, and if your not carful the same applies as it did for the silver. Honestly they are both prone to scratching if not taken care of, I just like the all black look a little better and do feel it may do a better job at hiding micro hairline scratches, we shall see down the line...but all in all these aren't caseless phones unless you really are one who doesn't mind your phone showing wear and tear...I'm just not that person, I like my stuff looking as good as it did on day one.