I finally did some side by side with the Play:5. From my ears, the Play:5 is definitely a bit more balanced, the HomePod actually seems to output more low end than the Sonos, to the point where it seems like it is exaggerating it a bit. Play:5 definitely wins in the mid-range - vocals have a bit more definition to them.
But I will say it is really close - without having them side by side in the same room playing the same song I wouldn't notice the difference. I don't feel the Sonos is worth $150 more, maybe if you get it at the price I got it for, which was $399. But then you lose Siri control and have to use Sonos software, which I'm really not a fan of.
One more thing to note - the HomePod actually works out better for my office that the play:5 is in, because of its circular shape. The sonos has its sweet spot on the other side of the room where my desk is, but sitting in the chair right next to it the homepod wins easily.