HomePod mini is certainly not the cheapest (Echo Dot, Nest Mini) and most people would agree that Siri is not as robust as Alexa and Google Assistant.
But it is certainly cheap enough, and to me, sounds better than smart speakers in its class (Echo 4th gen, Nest Audio).
If you are into Apple's ecosystem, it's a no brainer which is the right speaker. You get AirPlay 2, Intercom, Apple TV audio output, HomeKit hub, and iPhone hands off to name a few. And to me, looks a lot nicer than other speakers, including full sized HomePod.