A:Answer I would say it depends if you are more tied into Google or the Amazon eco-system.
My wife and I have had Google phones forever, as well as a couple of Chromecast devices, and Nexus tablets, also made by Google. It only made sense that we wanted to stay with Google products for an online assistant and speaker system.
We just got our Home Mini's the other day, and are still trying them out.
NOTE.. The Home Mini is free if you buy a new Google Pixel 2 or Pixel 2 XL (which we did).
As for the Amazon assistant, I don't own an Amazon Echo or Dot. However, I imagine they both can/will perform similar functions.
Hope this helps and Happy Holidays!