Of course it all depends on what's important to you, but I'll list some of the differences I've noticed.
The X is 6" shorter, more efficient, has Supercharger access now rather than next year, has auto-close doors, much better music options, has more comfy seats (for us, anyway), autopilot works in far more places, pano windshield, and it's got all the games, Netflix, etc. My wife prefers the X, but I think it's mostly because of the seats and familiarity - she's barely tried the R1S yet.
The R1S has more cargo space, a power frunk, far better off-road ability, better towing ability (including a larger battery, so towing might reduce range by a smaller percentage), easier-to-access hitch, built-in brake controller, a nicer interior, simple wiper and light controls on a stalk (but you don't need them because the auto operation is better), Driver+ seems more solid where it works, 120V outlets, compressor, cooled seats, and several other small niceties. The R1S is my first non-Tesla since 2009 and I've only had it 6 weeks so I'm still getting used to it, but I prefer it to the X.
The X sits lower and for as large as it felt to me when we first got it, it feels more like driving a car, where the R1S feels closer to driving a truck. Both are too big for me to find it fun to throw them in to a corner, so given that I'm avoiding that in both, I slightly prefer driving the R1S. (Over the X, that is. My Y, 3, Roadster and our S's were all more fun to drive than the R1S).
I think most people are going to be pretty happy in either vehicle!