I personally think the whole slider comparison method is pretty dumb - it makes direct comparison of certain image areas much harder (since you have to swivel your mouse around, not to mention how annoying this is on mobile) compared to a simpler solution where the whole image changes on mouse hover (which on mobile works nicely with a tap). This is how basically all screenshot comparison sites out there operate, and it really does work the best for the purpose of comparing two images like this.