The answer is simple. RTX 3060 Ti is currently the best card for mining, and is futureproof since it's an nVidia and can mine other coins, and the second-best is RTX 3070. Same hashrate/power as 3060 Ti but costs a bit more.

AMD's equivalent is RX 5700 (XT or non-XT, doesn't matter), but this card is EOL and is difficult to find. Plus it's an AMD so it's very difficult to set up properly. I own many AMD cards and I was finally able to breathe and have some free hours in my work day when I switched to nVidia. I had no idea they are so good and so easy to work with.