You can't go wrong with the Leupold or any of the ones you mentioned for that matter. I have always trusted Leupold, but have a Elite 4200(Bausch and Lomb) and 3200, they are both very nice scopes, the 6500 looks even better.
I have only heard good things about Sightron and Zeiss. Sounds like you have a tough choice ahead of you. I wish I could be more help,but I would also have a hard time with this decision. Are they comparable in eye relief? Do they have the same type of finish? Can you find any reviews?
The Elite and Sightron have more magnification, and the Elite also has the widest variable.
The Elite seems like it is a winner, I starting to convince myself as I type
Good Luck