The sensor of the NEX-7 is very demanding and I don't think there is an E-mount lens that can use all of sensor potential. The Sigma does a good job. Photos contain lots of detail and have good contrast. I'm not sure if it's better then the Sony 35mm f/1.8. I might be. From what I've seen so far, I'm not impressed by the Sony. But if you need stabilization and/or a faster aperture, the Sony can't be beat. The Sigma is ridiculously cheap. I got mine for 85 dollars (like new, hardly used and it even had warranty).