I would pick the Nikon over the Vortex any day. The Nikon is going to have superior glass.
I spent about 18 months researching this subject 3 years ago. Went to every store I could find within 200 miles that had a good selection of scopes. Looked through many, many scopes. Here is my opinion on the subject:
1. Vortex has a cult following. They do have great CS. They make quality scopes with a lot of features. HOWEVER, if glass quality is what you seek Vortex is not on top. Not even close.
2. For a varmint rifle you cannot go wrong with a Zeiss Conquest 6.5-20 with varmint reticle. Glass is amazing, and the reticle will help. Under $1K.
3. I had a Nikon Buckmaster in 4.5-14 that had amazing glass compared to Leupold and Zeiss. I paid less than $250 for the Nikon.
4. I have a Sightron SII Big Sky in 4.5-14. It has amazing glass that competes with Zeiss and Leupold VX3.
5. When folks say scopes are brighter than Leupold VX3 I wonder if they truly understand glass. Just like a TV glass can have a "cool" picture or a "warm" picture. Leupold glass is a "warm" picture.
6. You simply cannot go wrong with a Leupold VX3, Zeiss Conquest, Sightron SII or SIII.
7. I have a SWFA SS12x mil mil. Glass quality is disappointing, but it's build like a tank and has a nice reticle with great turrets.
Right now I have Bushnell 4200s, Leupold VX3s, Zeiss Conquest, Sightron SII big sky, Leupold Vari-X II, SWFA SS, and a Leupold VX-R.
Or, forget price and get a Swarovski.