I like both brands. I did however purchase the Nikon Prostaff 3x9x40and am very happy with it. My buddy and I both agreed that the Nikon had better optics. They both have life time guarantees. Although like I said I am more than satisfied with the Nikon, I am considering the Leupold for my next one in the very near future, same size, 3x9x40.
One good fact about Leupold is that they are made in the good old USA. If you are into that king of stuff.

Mac