I went through 5 windshields, fork lowers, and fairing wings trying to get rid of the buffeting on my Street Glide. So I think I can speak with knowledge on the subject of buffeting. BTW, I am 6'4" and long in the torso, so I sit high in the saddle.
The last, and best, shield I had on my SG was a flare from Long Ride Shields. That got rid of 80-90% of the buffeting. The remaining buffeting came from up over the tank, and unless you go with a shield such as the Madstad, you will probably never get rid of all of it. This is not as problematic if you're under, say, 5'10". The taller you ride in the saddle, the more of a problem the over-the-tank air becomes.
The issue is the vacuum created behind the windshield. If you've ridden behind a shield before, you know that there is a pocket of very still air right behind the shield. Nature abhors a vacuum, and seeks to fill that void. The flare shields do a great job of shoving the air up and over the shield, so the air to fill that void has to come from somewhere else. That somewhere else is up over the tank.
The Madstad shield solves this problem by leaving a gap between the shield and the fairing, a gap that lets in air and prevents the vacuum from forming behind the shield. Even as tall as I sit in the saddle, I get almost no buffeting with the Madstad shield. In fact, I'll never own another fairing Victory or Harley without a Madstad shield. That's how sold I am on their product.
I don't ride in the rain if I can possibly avoid it, so I can't address the issue of water coming up between the Madstad shield and the fairing. There is a gap there, which is the magic of how the Madstad shield works so well. You'll get more wind in your face with the Madstad should as opposed to a shield that seals to the fairing, but it's wind, not turbulence, and there's a big difference.
If you want the opinion of one who fought buffeting for 3 years on my Street Glide and finally gave up, save yourself the money and aggravation and get the Madstad shield. They don't look that bad in person. I don't give mine a second thought now.
2013 Victory Cross Country Tour
2" pullbacks, Tri-ovals, Madstad shield, TVS tuned
2014 Harley-Davidson Road King