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I would surmise a MK 4 10x or S&B would be the the best of 10x Fixed on big game ...SNIP...
I have a bunch of time behind the Leupold MKIV 10x. In my observations/experience, it is far from best. USO blows it away, as does IOR. Repeatability of turrets (tracking), and glass quality being the main factors.
That is opinion based on experience, and others that have used them may have a different view.