I've compared glass quality between my 4200 6-24x50 (30mm tactical), and my Dad's Monarch, and the Bushnell was at least as good. My dad and I both felt the Bushnell may have had the edge. Don't wory about Bushnell's glass quality on the 4200.
The bushnell has 12 MOA per turret revolution and I believe the Nikon has 8, The Bushnell is 1/4 moa clicks, the Nikon is 1/8 moa. Mine has 44 MOA total elevation (Bushnell rates them at 45 MOA total), I'm not sure how many the Nikon has. It's really all about personal preference. I think you'd probably be happy with either.