Between the 2 scopes you listed, I’d lean towards the Steiner, but I haven’t read any reports of either one on a .50.
I have read many reports over the years of of SWFA scopes on .50’s with pretty great results.
As far as rock solid build quality, mil-grade type options, the ones that immediately stand out to me are the SWFA scopes, Bushnell DMR/lrts, Nightforce NXS, Razor gen II, and possibly some Steiner offerings (and of course S&B and USO, but thats real money).
Meopta makes great scopes but optika6 is pretty new still, I’m hoping they end up with a great track record since they are priced so well.
All of those are great scopes, so warranty and service might be as important (on a .50) as the various small details and differences between them.
One other maybe worth mentioning in that vein is the Weaver 3-15x50, though not sure where they’re currently at as a company.