I've tried both, so can give my thoughts if it's any help.
A while back I replaced my five year old Play with two Sonos ones and paired them up. They sounded really good: I was surprised. Then I went a bit crazy and bought a Sub. This is because I had future plays for a 5.1 sound system, and also because I was mad curious on how they sounded with the stereo pair.
The answer is awesome. I had the Sonos 1s on a bookshelf, about 8 foot apart, slightly above ear level (when I am sitting on the sofa). The sub delivers lush, immense bass. My god it's beautiful. That said, I felt the Ones were lacking in range; the highs felt strained and the mids a little fuzzy.
After reading a lot about the HomePod, and as I'm only Apple Music, and also because I'm 100% committed to Apple kit AND after reading about HomePod and stereo pairing after iOS 11.4, I thought I'd give them a try.
And so, from my purely subjective opinion, the HPs sound significantly better. It's the verticality of the sound. The music feels like it is being beamed into the centre of the room. As I'm sitting now, facing the speakers, the music is coming at me right from the middle. It's great. Even if I sit on my other sofa on the side I feel like I'm hearing so much more from the music. The science of it all eludes me but I've had a lot of fun listening to music with it.
The Ones, on reflection, felt much narrower, like I was listening to a horizontal gap of music (sorry, best way I can explain it) and I had to sit in the right position to get the full effect. The HPs by comparison just fill the room. The bass obviously won't be as lush as the Sonos Sub, but it is surprisingly good, even if a little overpowering at times. But hey, I like my bass. It definitely isn't a neutral sound. Given the price I would expect a much better sound - which they deliver.
The Sonos ones will become the rears when I eventually get a Sonos Beam.
(anecdotally I've found Siri much better than Alexa, and seems to do the simple things much better. I love the fact I can tell Siri to play in my lounge and in the bedroom - where I have an Airplay 2'd Sonos One - and it works really well)
Hope this helps!