Please fill the questionaire first
But Im putting my views forth first anyways
Moto X Play is the better choice here
Simply because its got a better camera, better developer support, more popular model than Nexus 6 was since Nexus 6 sales were actually low(helps in dev support and parts etc), Better materials,64-bit cpu(may not be relevant for 2 years imho) etc
Only thing in favour of Nexus 6 is the Snapdragon 805 which is a more powerful chip even if its a 32-bit one