The only thing the Nexus 6 has going for it over the Motorola Droid Turbo is stock Android, otherwise the Motorola Droid Turbo is just a much nicer phone, better build materials, 21 MP camera, huge 3900mah battery, and it is a reasonable size, if you call 5.2" phones reasonable, but that is the trend nowadays, the Nexus and that huge 6" size is a deal breaker.
For me it is the Note 4, it has everything these other phones have plus more, including Micro SD card expansion and removable battery, and a proven track record in the phablet category of smartphones, my second choice would be the Motorola, if the Nexus 6 was a bit smaller than it would warrant my attention.