Now that fritzbox has released an update which supports mesh networking. I have brought a second fritzbox and am going to go with that. Google wifi is the better and more secure system but two fritz boxes is simpler and means i have less stuff in my server cupboard.
They look like this:
https://www.pbtech.co.nz/product/NETGOG0158/Google-Wi-Fi-Mesh-Wi-Fi-System---3-Pack
Purchased in april this year from pb tech and i can supply a copy of the receipt for the warrenty.
Asking $400 including shipping.