All three scopes are withing $100 of each other.
The reason I was headed for the Viper HST instead of the Diamondback Tactical is two fold. Although the HST is more expensive, It also has much nicer feeling turrets and a zero stop. Although with the HST It is only offered in Second Focal Plane, But that is not really a deal breaker for me.
The US Optics TS12-X is the one I really want to compare to more popular optics, because everything else they make is generally considered to be a tier one optic. The TS line being their more affordable option is still bound to be pretty awesome, considering the reputation of US Optics.