Jon,
In terms of plain face shields I have used the Huntsman and Willson flat wraparaound styles and prefer the Huntsman. The Willson shield seems to be of softer plastic and has given me trouble when cleaning it. I also prefer Huntsman's mounting method.
From another direction, I also have a 3M AS200 powered respirator that I really like. It has a blower and HEPA filter built in. I consider it a real lung saver, especially with spalted woods. It takes a little time to get used to the size of the unit but I now use it for almost all dust-producing processes in the shop.
David