I don't have any experience with the Venom, but Vortex seems to have a mixed reputation. Their glass seems pretty good to great, but I've heard multiple stories of the cheaper scopes not holding up. Maybe their QC isn't as good on cheaper scopes.
I have a Venom, It is OK. I am automatically biased as it is MOA and I prefer Mils. I dont think the clarity is great in comparison to my Riton scopes. If you are getting it in the $3-400 range it is acceptable.
