Run 3dMark Vantage, see what you get. Some cards run better in some operations than others. That stability test does not really test out the capability of the cards.
Think of it like the Mario Cart cars. You can have a car that is fast in acceleration, it will beat a slower car in a straight line, but once you hit curves it will fall behind to a car with better cornering and balance. What you need to do is run a test that tests many functions of the card not just a few. I have run that stability test before, and it's a pretty simple thing, not really made to benchmark cards, just heat them up to see if they crash.