I have a couple of Buckmasters and quite a few Leupold scopes. One of my Buckmasters failed last year and had to be replaced by Nikon, but out of all of the years and all of the scopes I have not had a Leupold fail yet. I think the new model VX2 is a step up from the Buckmasters and a 4x12 can be had for somewhere around $400.
If you can add more to the budget (not always possible!) the 3.5x10 VX3 runs somewhere around $480 and it is a great scope. That is the scope that currently sits on top of my .300 WM elk rifle.
Surely some of our "optics experts" (a few are on my Ignore list) will chime in soon to recommend their favorite brands in place of the two that you inquired about. There are many good choices, but you will not regret buying the Leupold.