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General rule if you want to compare against the database is use performance. If comparing yourself between your old or new card, it doesn't matter what settings so long as both are the same (I usually do default)
If you are trying to get points on hwbot for example, pointless running it at anything but performance as your score will be too low.
I ran Vantage the other day for the first time in a couple of years because I have just bought a GTX 470.
I ran it at default settings this time but this thread has reminded me i used to always run it at performance.