I have a ASUS zenphone. I am still running Marshmallow 6.1 on it and the speed of my smartphone is not upto the mark. Can upgrading the operating system helps in speed. Recently I read the article on Android 7.0 Nougat Vs Marshmallow and found that ONLY pixel and nexus mobiles get speed and performance benefits while other phone will run on same speed on updating the software. Is it true? Please advice me whether I should update my phone.