I was at a dealer's table at a gun show who carried all manner of scopes. He had everything from Leupold, Zeiss, Swarovski, Kahles, and Schmidt & Bender.
Zeiss, Swarovski and Kahles were nearly identical in clarity and brightness. There were differences, but I couldn't pin it on model or manufacturer.
The Leupold was a small step down. It's quality glass and I thought it was nice until I picked up the others.
I had never heard of Schmidt and Bender (S&B) before and I didn't expect much considering the big three that I had looked at were nearly identical, but the S&B glass was MUCH brighter and clearer. Even the optics geek that I brought with me was impressed.