window deflectors

Well, I think you've posted in the wrong area.

With Pearl, a GII, the "deflectors" do reduce the wind noise, but you still get some wind noise.

As far as rain, they stop it from coming in except a bit still will get in at the front, where the deflector actually ends -before- the window opening. It only comes in there when stopped, and falls harmlessly on the plastic door panel.

 

I got these for our 2010 Prius:

WeatherTech Automotive Accessories - Side Window Deflectors - 2010 Toyota Prius - WeatherTech Side Window Deflectors, Vents, Rain Guards, Wind Deflectors

The front ones extend from upper back corner to lower front corner of the window, so no rain gets in when the front window is cracked.

 

I have WeatherTech on my gen 2 and they work well to reduce (not eliminate) wind noise and allow windows to be cracked open in rain. The back ones do have a gap at the rear due to the shape of the window frame so I only crack them open a tiny bit when parked. The front windows can be opened more. If it is very windy then rain and dusts can be driven into the cabin so I don't crack open the window too much when it's very windy especially when I park and leave the car.

 

We had deflectors on a previous car. I don't regret getting them, but after a few years experience with them resolved to not do it again.

They do a allow you to crack windows without rain getting in, and reduce wind noise a bit. OTOH, they make car washing slightly more hassle, and being plastic they tend to get increasingly burnished looking over time.

Depending on fastening method they may also start coming loose. At least with our car, install involved some cutting of weatherstripping, and use of adhesive strips, so it might be expensive to remove them and restore the windows, down the road.

 

I got mine off ebay and they are great for leaving the windows cracked but there is an uneasy feeling with them. I am still not adjusted to what seems like a huge blind spot. Maybe due to the dark tint on the ones I got but the additional 1.5 inch on the front pillar is scary from my seating position. I now feel like if a pedestrian walks out on my driver side I will not see them which now has me extra cautious.

 

No kidding, that huge A-pillar the Prius has doesn't help, but just pay attention to the road and you should have no problem. In time you'll get used to it like I did. For now, move or tilt your head a bit when you feel you're in a precarious situation.