Foxcaller,
The Nikon Monarchs are very similar to the Elite 4200s as both have 95% light transmission. The Nikon Buckmasters are similar to the Elite 3200s as they both have about 88% light transmission.
But light transmission is not the only thing to look at when it comes to scopes. You should also look at resolution and clarity, and, of course, strong construction and warranty.
In my opinion, the Leupold Vari-X IIIs are great, but overpriced. I don't like the VX-IIs because, as I believe, they have a TWO piece tube (the Monarchs, Elite 4200s and 3200s, and Vari-X IIIs have a ONE piece tube.)
I have several Monarchs and have NEVER had any problems with them. In fact, I own several Nikons that are pre-Monarch and they have also been Flawless.
The only advantage that I see with the Elite 4200s is the rainguard feature. Other than that, the Monarchs are hard to beat.
Zachary