I like the clarity of the Monarch. My exposure to Nikon has been limited to a 3-9X40 UCC on a 22-250 in the Arizona sun but I'm impressed. The controls are smooth and accurate. The quality of glass is very evident if you've owned less expensive scopes in the past.
The Monarch is sitting in replacement of a Bushnell that had so-so glass and terrible controls. In Bushnell's defense, it was a variable with A/O and BDC but not their top-of-the-line Elite series.
The only Burris I'm familiar with sits on a 12 gauge slug gun. It is a pistol scope, however, and might not be a good comparison to their rifle scopes. It does have very good glass though. Not as bright as the Monarch but good enough to touch slug holes at two hundred yards. Not my shooting but my brother's
. I witnessed this.
I would go to the local store and check out the optics of both indoors and outdoors. Your interest is in a variable so the controls should rank high on your list of concerns, also. Just because you can see it doesn't mean you can hit it if the innards are mediocre and you can't repeat your adjustments.
I think there are a lot of good scope manufacturers out there. Some are even the lower priced brands that the die-hard expensive scope guys wouldn't touch with a stick. You know, the ones that insist that the scope should cost as much as the gun. Of course, there are expensive scopes out there that don't deserve the price based on my readings (not first hand knowledge) but I don't think Burris Signature and Nikon Monarch come close to falling into that category.
It all comes down to your expectations and wallet. Good optics are like a beautiful woman. They both cost money. The only difference is the glass is an one-time expenditure.
