I have 3 Vari-X-III, 50mm's, and have been pleased with them, but I had an experience a couple of years ago that opened my eye's(no pun intended). A friend of mine purchased a 3.5x10x50mm Weaver Grand Slam and said that he thought that it was "brighter" than a comparable Vari-X-III. I told him that I had some doubts about that. He asked me to go deer hunting with him and sit in one of his "condo" stands so we could compare scopes side by side.
Before going further, I need to say that here in SC you can legally harvest a deer up to 1 hour AFTER sunset. Consequently, high performance low light scopes are very important here. To make a long story short, we watched deer from about sunset until dark, comparing his scope to mine. We particularly watched a small buck at about 100 yards until about 50 minutes after sunset. At that time I could still count points with the Weaver while I could barely make out the deer with my Leupold. Needless to say, I was embarrassed that a $300 scope clearly out performed my Leupold.
In case anyone is wondering, we tried to do everything that we knew to make the test fair including cleaning the lenses, and comparing on the same power as best as we could tell.