The one thing you can generally count on is that diamonds graded by EGL are somewhat discounted based on the belief that the grades are a little looser than AGS or GIA. Occasionally, a diamond graded by EGL is very must graded like a GIA or AGS lab graded it and that particular diamond might be a better value than expected. Now, this is a rather rare occurence, but we have found it occasionally. I believe the cut study posted on Pricescope of the 17 diamonds submitted to the various labs brought out this point in its findings.
So, it isn''t all a bad story. Proper shopping and looking can reward an open minded consumer on occasion. No lab is 100% accurate in color or clarity grading. They do the best they can with their eyes, but the "standards" are subjective judgments.