Ate you going to be dialing in, or holding over on your elevation for different distances? The SS will probably be the most repeatable/reliable scope in that list if you plan on doing a lot of cranking on your scope. For some odd reason the 16x SS is noticeably brighter than the 20x (exit pupil) in the SS scopes that I've looked through.
I would tend to give the Nikon the nod in terms of glass quality. For around the same price as a SS you can still probably find the 6-18x40mm with mildot reticle. Might be the way to go if you are going to hold over for each shot, but the reticle is SFP and not FFP, a handicap for hold-over guys IMO since you will effectively turn a variable power scope into a fixed power, otherwise your POA/POI will be off.
If you have a hard time picking up smaller objects at closer ranges try aiming in with both eyes open (bindon aiming concept), you will be surprised how much faster you can get on target. You can always close your eye when the time comes to actually shoot.