I think between me and Micky we have tried or owned nearly every scope available for HFT.
I own three Sightrons with the slightly earlier ret as I prefer the aimpoints for a 30 yard zero.The glass is superb but they are not the best depth of field, which is good if you use blur, not so good if you dont. You can tell exactly where your PX distance is within a yard which is really helpful to give you a marker point. I always re zero my turrets and up to now have only once caught a top turret in three years.
I have looked through a few Vortex vipers and they are very impressive and to my eyes are virtually as good in glass quality, with a better distance over which you have a clear picture. I would think of which would suit your style of shooting best and go with the most suitable of the two.
The only other scopes I have taken to are the smaller Burris scopes and my Mk4 Leupold with TMR ret.
Mickys Nightforce scopes are a bit too clear for me and how I shoot.
Sounds like you will try both before you buy so it depends on your eyes and what you feel best with.