Here is a selection of footage shot of the same shrimp ('Little Green Shrimp' Phycocaris sp.) using 2 setups. The Canon 5Dmk3 with MP-E 65mm set to 4x lifesize magnification with a Nauticam housing, and a Canon 7D with 100mmL and stacked 10x & 5x Subsee Diopters. As you can see the magnification is about the same. Can you see a difference in image quality?