We kind of went off topic there, this is about cat crap. Which I would like to hear more about because this would solve many of my problems.
Now to contribute to where the thread went.
Goggles: Keep the wind from pushing your eyes back, allow the use of glasses underneath, protect the eyes better, limit vision
Sunglasses: Lighter, some wind will push against the eyes, small debris can come in, fall off easier, allow full use of peripheral vision
Both: Keep the sun out of your eyes, or enhance vision ever so slightly.