<p>First, set your current zoom to 200mm, look thru the viewfinder and zoom out to 300mm. If that makes a big difference to you, then your decision just got harder.</p>
<p>For me, it is not much of a difference. If you can't get the shot at 200mm, the likelihood you will get it at 300mm is slim.</p>
<p>For me the 70-200 IS f2.8L is a great lens, not merely a good one, and is one of the finest lenses I have every used. I have used it with a Canon 2X and the results were amazing.</p>
<p>Ed</p>