That's not true.....Nexus 6P at half the price of a comparable iphone will not lag. It will get all updates from the source and be ready out of the box. There are a ton of cheaper Android phones that compare both in performance to iphones that do not lag and are ready out of the box.
The UMI Super is $179 and compares to the iphone is specs and design. It doesn't lag and performs really well.
http://www.gearbest.com/promotion-umi-super-sale-special-644.html
As cheap as a Nexus is I don't like it at as a cheap phone because it's Googles Flagship device meaning high end. I'm taking about like the new Samsung J5, Samsung J3, the Xperia X stuff like that. I've watched unboxings and reviews guy turns the phone and immediate lag