But then it's not really about the one single Google Wifii unit being as strong as the OnHub. The idea behind Google Wifi is that multiple units working together as a mesh network can do a better job of covering the area than a single point solution like OnHub. Whether that will actually prove out is the big question.
For normal home use, those 13 antennas really don't do anything - 2 antennas (one shooting more-or-less vertically, one horizontally) will give you good coverage in a 2 story house. (No wireless router will cover much more than that. If it does, it's just luck.)