Polishing props is dumb IMO. A little texture inhibits air flow separation resulting in smooth and efficient laminar flow. Take the golf ball, a blunt flying object. By adding dimples and tripping the laminar boundary layers - reduces drag. Airplane wings and our props are less prone to separation since they aren't as "blunt" and as a result skin-friction drag is more important.High gloss makes them less sticky with regards to the air/skin boundary. More noise and less efficient, though the numbers are very small and in my opinion insignificant. You want the air to stick to the surface.
Take a look at this video and prepare to have your polished mind blown.
And what about golf balls (I knew you were thinking it)?
Why aren't airplanes like golf balls?
There does exist other types of devices commonly used on wings that create a similar effect to the dimples used on golf balls. Though these wing devices also create turbulence in order to delay flow separation, the purpose is not to decrease drag but to increase lift. One of the most popular of these devices is the
vortex generator.
A Gloster Javelin showing the three sets of vortex generators located along the outer portion of the wing
I've sanded with 600 grit and left it at that. Wow, what an improvement! I'm just not convinced I should be waxing/polishing my props. I recall while in college learning a little about he physics of air flow over curved surfaces; aircraft wings - where by keeping the air attached, smoother airflow and better lift resulted. High gloss doesn't help keep the air attached.
Maybe that rough trailing edge will act as a spoiler like we see on the Subaru WRX? ;-P
I've read the polished props are best for keeping bugs from sticking. Definitely a benefit there, especially if you live/fly in buggy areas. Not a big problem here in Colorado. If you live in a buggy area, I suggest keeping a "Magic Eraser" in your kit.
Seriously, these drones use brute force and a little sanding here and polishing there isn't going to amount to anything that can be measured. But if it floats your boat go for it. FWIW, I do sand down the flashing and ridges that often accompany DJI props.