Splitting hairs.
There are not many scopes that I would trust over the Steiner durability-wise, but it is well documented that they are not the best optically.
I have limited experience with the MK5 but to my eyes, both have reasonably good contrast, resolution, and brightness. Both also have piss poor CA control. I would place them on par with Razor Gen 2 or slightly below, but in no way superior.
Turrets are vastly different. Very fine clicks on the M5Xi due to 12 mil revs, and there is absolutely zero slop. The MK5 has a locking detent on zero along with 10 mil turrets, but there is noticeable lash between clicks. One is not necessarily better than the other, they are just very different.
Ultimately, I would recommend you pick one based on your reticle preference and cost. For me, the SCR/SCR2 blows any of the Leupold offerings out of the water, but I would certainly not be paying a premium for the Steiner if I could get a Leupold significantly cheaper.