Here is my process for new cards: Pick a pricepoint, head over to Video Card Benchmark and scroll down until you find the first (ie fastest) video card that meets that price point. Also double check prices at PC Part Picker. For used cards, the chart is still pretty useful, just a bit more manual (and money saving!) to get used prices from eBay/Mercari.
I personally have an AMD bias though, since they have pulled way less shit than nVidia. But, that is your decision to make.