Leupold? Let me count the ways? Rather than spend lots of money on a stock car that does not improve the quality of thier products IOR buys T* Zeiss coated glass. That's the stuff in top camera lenses. Leupold has the the eye relief set so there is not as much field of view. Most of the 6x Euro scopes have as much wider field of view as much as a 4x Leupold, which makes them a lot more hunter friendly.
In the 70's nobody had heard of Toytota, but thier detroit steel was rusting in the gas line too... That's kinda where Leupold is today. For the money you can get a better product, but there is not a dealer on every corner. Leupold has good service, but why should you need that? They have glass that is not as clear, which is the main grip for most of us. Zeiss Conquest line is priced with the Leupold stuff and has the same level of service and is a better glass.
For 6x I see it this way: Sightron if it is still listed, IOR, and then Zeiss. The Kahles 6x is harder to find now and about the same money as the Zeiss, so I'd go Zeiss.