The Buckmaster has slightly better glass. I was in the same boat when I picked up a Weatherby last year. I was able to compare both side by side, outdoors on both cloudy and sunny days and the Buckmaster was clearer all around. You may not be able to see much difference indoors, but outdoors it is easy to see which is better. With all that said, depending on your budget, I'd look at a Monarch. They are even better and comparable IMO to a Leupold VX-III as far as clarity. I'm not sure of the longevity, however, which Leupold is known for. In my situation my budget called for the Nikon Buckmaster instead of the Leupold VX-II and So far I am quite happy but I do think my Leupold VX-II on my Ruger is better. Sorry for the rambling, hope this helps.
I have the Nikon Silver Prostaff (3x9x40) that I like. I've looked through the Buckmaster, but only indoors, so can't really say that it's better than the Prostaff. I think you can't go wrong with either scope.
Get a Leopold I love mine and it is a fixed 7 power! no seriously both are good quality scopes I was going to buy a pro staff 3x9x40 until my buddy said he would trade me the Leopold for an old CB radio I had in my truck. I still use the scope the radio gave him 2 weeks before it fried.
The cheaper one! What caliber rifle is it going to sit on? the answer is the answer. If it is a heavy recoiling cartridge you will need a step up to handle the recoil. I had a scope that would not hold a zero on my .30-.06 but it did fine on a Friend's 222.