I've got the older Nikon Monarch (1 year old - the last production of the older models that were on clearence everywhere last year) and the Leupold VXIII (3 years old). The Monarch is pretty good, but IMHO the VXIII is better. I think the light transmission is better and I think the eye relief is better. I think the Leupold has better resale value as well.
Shoot straight and always carry a 7mm Remington Magnum.