RE: Couple of scope questions
Buy the Nikon, without a doubt.
Bigger objectives allow more light to enter the scope. More important is the quality and completeness of the coatings on the lenses. The Monarch uses the Ultra Clear Coat system to fully multi-coat all the lenses in the scope, and this give the Monarchs a remarkable 95% light transmission. A good fully multi-coated scope with a 28mm objective can easily get more light to the eye than a lesser scope with a 32mm objective.
Also, the higher the magnification, the less light that gets through the scope and the dimmer it will be.
I'd also recommend the Nikon for the lower magnification. 12x magnification is not, IMO, beneficial with a pistol that is already unsteady, and the effective range of a pistol doesn't warrant that much power anyway. The lower magnification will allow a steadier scope picture, and 8x is plenty for shots out to 150 yards.
Mike