I just do it in Sketch. For me, any evolutionary insights are secondary to shipping, so I'd rather stay on the golden path of tooling than adapt the flow just t

I just do it in Sketch. For me, any evolutionary insights are secondary to shipping, so I'd rather stay on the golden path of tooling than adapt the flow just to see changes. However, it's generally pretty easy to simply zoom out and see your evolution just by looking at multiple artboards at the same time (the changes I'm interested in are more about feel and aesthetics, so I don't really need any pixel level onion-skinnng or anything to compare revisions). FWIW though, Github's image diff is quite useful in this regard. They have a number of useful comparison interfaces for image files that may fit your needs.