I'm a Vortex junkie...I have 4 Viper PST's (2 GenI, 2 GenII), a Diamondback Tactical, 3 pairs of binoculars, and 2 rangefinders....
Anything labelled Viper has better glass than Diamondbacks. Depending on physical features and generational differences, the difference may be pretty small, though.
The Diamondback Tactical is the 4-16 FFP, and at $350 street price I think it's an amazing value. It has a graduated "Christmas tree" style reticle in either MOA or Mils that makes holds for distance and wind a no-brainer. It may suffer a little at lower light levels, but I haven't seen it yet.
That said, if you're limited to 200yds or less and have no aspirations of shooting farther, it's probably unnecessary complication.
I personally have no experience with the Athlon, but generally hear good things.