I also have a Leupold 3-9 Vari-X II AO. Also a 6.5-20 Vari-X III and a 8.5-25 Vari-X III.
I have a Simmons Gold Medal 6.5-24.
My buddy has a Nikon 6-20(?).
All three are very good scopes. I would rate them as the Leupolds in 1st place followed by the Nikon and Simmons Gold Medal tied for 2nd place.
I don't know about the White Tail Hunter, but at $99 I wouldn't expect it to be up to the quality of the models mentioned above.
Bear in mind there are other high quality scopes on the market, but of the ones you mentioned, this is MHO.