From a performance standpoint, well, it would be the card that I have currently because I've never owned one of the top-two most potent video cards in the world before. I have to admit, it's pretty damn awesome!
ASRock Radeon RX 7900 XTX Phantom Gaming OC:
From a design standpoint, that would have to be the XFX Radeon HD 4870 because I love that spiky goalie mask look (which is why I made it my avatar). I have both iterations of that card:
They also came with the coolest and most badass-looking video card box-art that I've ever seen (IMO of course):
Video cards today look kinda bland compared to the cards of old with that came with the wicked box art and graphics on the cards themselves. Today it's all boring designs and RGB.