Well, most of the radio bits are from Qualcomm, not Motorola.... they are all built into the SoC these days. Motorola has to fuss with the radio firmware and all.
Would I buy this phone again right now? perhaps.... I guess the a hesitation would be the new Nexus models that are looming on the horizon. They are still mostly unknowns at this point, so it is impossible to make a fair assesment. And there is also the new Moto X Pure Edition that's also waiting in the wings. But the Huawei Nexus and Moto Pure are really the only two upcoming phones that even draw my attention.
But, as far as stacking the Nexus 6 up against anything else in the market right now, yeah, I wouldn't pick another phone. No reason to. It still performs on par with the newest models. I've been running M since shortly after it launched and I am quite pleased with the new features. Other than "because different/new", no compelling reason to switch.
Though, I kind of like my wife's G4... software is a little meh, but the camera and form factor are pretty sweet. Nice phone. Wouldn't switch, but still nice phone.