I'm not looking to spend $350, but if I was, honestly Siri would primarily need to be as good as Echo or Google at controlling smart home devices for me to care about that comparison. And having used all three for the last year as I've been installing smart bulbs and plugs and Harmony stuff, I'm not worried about it.
If Siri in HomePod is good at working with the Home app, Hue, Harmony, etc and controlling other Apple devices and services, then it would do the job just fine and in some cases better than the others