Window phones are the smoothest, even more smoother than Galaxy S7, Note 5, iphone 6S etc.
Calling me a nutcase?. If you do, you are probably kidding yourself!
When it comes to smoothness and stutter free day to day performance, windows phones spank these Snapdragon 810, Exynos 8890, Apple A9 super powerful chips with their snapdragon 400 series quad core chips!. They are so fast and smooth, even with mediocre hardware.
There is price to smoothness ratio too!
I use Lumia 640XL on windows 10 mobile preview for day to day tasks along with Android flagships and it never made me feel that its strictly a lower midrange phone having just a snapdragon 400 chip. I see animations stutter slightly in many Android flagships, but never seen one in my Lumia. Multitasking is lightning fast, no hanging, no lagging in general day to day tasks.
When it comes to photos with flash, the Lumia rich capture with dynamic flash feature is something so awesome which is neither in latest Android flagship nor in iPhones. Its hilarious, my friends holding iPhones and latest Android flagships want me to take their photos in dim lights with dynamic flash, so that flash can reduced, removed, or added back to photo later as per their liking.
Windows platform has its own limitations, but lumia rich capture with dynamic flash, pro camera controls and price to smoothness ratio is where it shines a lot more than its competitors!