Turntable vs Spotify through Sonos speakers - who can tell the difference

Yes. Spotify won’t have all the pops and crackle that are inherent in records. It also won’t have the high distortion inherent in records, especially as the arm gets closer to the inner grooves. Spotify will have a higher dynamic range, though most rock/pop recordings don’t take advantage of it. 
 

If you want the “enjoyment” of physical media, get a CD player. 

Yes, you can hear a difference between vinyl and streamed audio, but if your turntable is set up well and it’s all going through your Sonos system it might be more subtle than you’d expect. If you’re considering adding a turntable to your Sonos system, do it because you enjoy collecting and playing records, don’t do it expecting a dramatically different sound.

I absolutely appreciate the convenience of streamed music and these days listen that way more often than I play records, but flipping through my physical library is definitely more satisfying than scrolling through lists on my phone. It’s a library built up over the last 30+ years though when vinyl was relatively inexpensive, and there are a lot of good memories tied into it.

I wouldn’t let comments about pops and crackles turn you off if it’s something you’re really interested in — I get some of that especially with used records that I bought in less than stellar condition, but most of the ones I bought new in the ’80s and ’90s still sound great. One thing I really appreciate about them is that they still sound like the music I grew up with. Sometimes I stream an album that I’ve been listening to for years, and recent remixing/remastering will emphasize different elements in the mix and sound jarring to me, whereas my physical copy will sound the way it always has. This past weekend I was streaming a greatest hits comp and the songs weren’t level matched, it sounded like they’d just been grabbed from various sources and strung together as a playlist; my almost 35 year old physical copy may not sound as crisp anymore but it’s a more pleasant listen as the songs were mastered at similar levels for that version of the compilation.

I only buy a handful of records every year now; they’ve gotten expensive and I’m running out of space, but it’s a way of supporting artists who I know are only getting pennies at from my streaming. And it’s still a nice way to listen to music.