I have a Sightron SIII and a Vortex Viper HST. I've used Sightrons warranty, have not used Vortex warranty.
And I would agree, the HST would be a better comparison to the stac. I don't see anything that says the Sightron has ED glass, the vortex HST does, it also has a zero stop. If the HST would also be a consideration I would chose it over the Sightron.
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