The more stress a plant has been under the more flavornoids it tends to produce. These differences are not insignificant, since researchers have found that the amount of flavornoids, within the same variety of different samples of sweet cherries, can vary by a factor of at least 3. So fruits, nuts, and vegetables that have been attacked by insects and subject to bad weather conditions are very likely healthier for us. In the end, farming methods that mimic natural conditions are probably the best. This is, of course, just another example of one of the benefits a hunter-gatherer lifestyle once gave us.
(Stressed fruit may be better for you by Jennifer Viegas)