Michael Linn , Aug 13, 2011; 11:13 p.m.
I would recommend holding them up to a strong light source (not the Sun!) and looking through them carefully to see what is inside. If one if them is much clearer than the other, regarding dust/cloudiness/etc. make your choice based on that. If they both look really good, flip a coin. If they both look pretty challenged, look for a different lens.