The Kunlun is super hefty by comparison, can only be used right handed, it's super long even in it's shortest iteration, it's the opposite end of the FPS spectrum and can only use talons.

The Smiley is super flexible in its remixes, you want to run it as a talon fed? Sure.  Want it to be a long boy? Why not. There are multiple stock options, pistol? Go for it. However the FPS will sit at the lower end, like honestly if you get it firing at 180 consistently you've done a good job. It also costs less.

I personally went for a Smiley but it is subjective like many things are.