I used these two lenses on Canon 5D2 at a recent wedding and here are my observations. 1. Image stabilization didn't come into play often because I used 1/125" to freeze people. Subject movement ruined the picture. For still life, image stabilization is useful. For handheld macro, it was essential. 2. F/2.8 blurs the background better than f/4 and makes the subject pop. The larger aperture also shortens the shutter, which is often necessary. 3. Both 70mm and 105mm are too short for candid shots and head shots. 135mm was just right. I never found myself in a situation when I needed 200mm or longer. 4. No matter the lens, I needed a powerful flash that recycles fast. I used 580EX2 and bounced off the ceiling or walls. Fill light produced crisp pictures that I couldn't always get with high ISO and large aperture only. 5. Although most of the images were made with either zoom, I couldn't justify bringing only one lens to a wedding. I needed a dedicated portrait lens with some reach for beauty shots and candids. Of the shots I kept, 70% were made with the zoom, 30% with 135/2 and a few shots with 100/2.8 macro IS. All of the macro shots are among the best of the album. Images from 135/2 are often superior to either zoom but the zoom is invaluable to tell the story.