Opinions are like assholes -- everyone has one and everyone's stinks.

What windshield you buy depends on how much protection you want.  I had a National Cycle Flyscreen and a National Cycle Street Shield -- for reducing wind on the torso or reducing wind in the face.  If you want more protection, you can use one of the Plexifairin/Plexistar screens.  Or similar from other manufacturers.

Once you have the windshield, you can trim the top or add a little.  You can mount the windshield up or down a little.  On my Savage on the Street Shield I mounted it about 1.5 inches over the headlight.