boatdoc,
I've got a 3.5-10 VX111 on a CZ .375. The 3-9 is a VX11 BTW. It would work too. Since I think of the .375 as a hunting rifle, not a DGR, the 3.5-10 a good fit. Despite what a lot of people find, the low range variables don't do much for me. Anything under 3 is a waste to me, as I've had them and never used the lowest powers.
I have a 3-9 Zeiss Dia-vari on another .375, this one a Remington. So far I have gotten away with it, but the eye-relief is right on the edge of safety.
I also have a 3-9 Conquest and it doesn't hold a candle to the Dia-vari. That one sits on a .308 and will stay there. That bulbous occular bell takes up a lot space that I need, so I've been grazed by that little pop-gun. Of your choices I'd go with the Leupold. Stubblejumper will be along shortly to say the opposite.

Which Leupold rings do you have that you need a leatherman? I have Leupold Qds on one .375 and Warnes on a couple big guns. No problems with either.