I had to laugh at myself when I was looking at the differences between the two examples and I didn’t even notice the obvious colour difference in the orange buttons!
You have to be careful using words like ‘better’ and ‘worse’ when it comes to design since a lot of things are judged by the current cultural aesthetic (unless you believe in some platonic absolute).
So one of the designs when scaled down has edges that snap to pixels to create a sharp border. Some designers will find it very satisfying to create a design that defined down to the smallest possible unit (in this case the pixel) I think this satisfaction increases with higher resolution displays like the retina. Others may find joy in a generative design where they set loose parameters and see what occurs. Others again may embrace chaos and like to randomly apply a texture for instance.
And of course designers influence and are influenced by each other so we see periods of style where something is first fashionable, and later will fall out of fashion when it becomes too common. Often this is driven by technology because designers love experimenting and like to push boundaries of what’s possible.
In terms of the two designs shown, I do have a preference for the optimized version with sharp pixel-snapped objects and appreciate the skill that went into that, but then again from a pragmatic point of view think that the difference is so minimal that for the number of people now and in the future that are on a non-retina screen it’s probably not worth the effort (or the extra ~25% asset file weight) unless you have the available time.