Well, for sure they absolutely protect the leading edge of the hood from chips.... Yes, they give the vehicle they are on a different look.... a bit of contrast which is often a plus...
Do they deflect bugs and maybe even small pebbles...... sure undoubtedly they deflect a few but to say they deflect all or most might be deemed laughable by many.
With that said... I truly like the one I installed a couple of years+ ago.. 36,000+ miles.
It has weathered well, not faded or come loose. It has deflected some bugs and pebbles... No chips on my hood..
The one I purchased installed easily and has NO logo, again no logo on it which was important to me. I purchased for the look and not necessarily that it would be truly functional..
Bushwacker 14093 Trail Armor Hood Stone Guard Black Textured Finish, 1-Piece for 2018-2021 Jeep Wrangler JL, 2 and 4-Door.
I have had the low one like pictured by Rhinebeck01 and went through two windshields. Then I purchased another one that is higher and has more of a bulbous shape that points up(you insert these rubber bumps in back of it to strengthen the shield) I can actually say I witnessed a small stone get carried up and over the rig!!!! Now It may not always ...but in this instance I Was very happy not to be ordering another windshield. I actually just installed the Racing Optics tear away laminate for the windshield also. So hopefully the cracks/ chips and bull shit of replacing it every other month is done. I Keep my rig clear from others when driving.. never tailgate..never drive behind any Trucks and yet the screen is a magnate for stray debris. So in short I do believe the hood contraption helps reduce the amount of debris the screen normally would intercept.