My favorite nano is anything that looks good that isn't super expensive. I still think the ADA tanks with all the fancy stuff look good, but I prefer other tanks because they can cost a lot less and look just as good. You can get a rimless tank that looks nice for a fraction for the price of an ADA mini M or S. IMO it's not worth it to spend 2-5x more money on something that has the ADA brand. My favorite nano that I have right now is my Fluval Spec. I like it because everything is hidden in the back and you can even fit a heater in the back. The LEDs it comes with are just ok, but you can get better lights for a good price and grow more plants. I see how ADA tanks can be an "aesthetic element" in a room or home, but it can be easily done with many other tanks. In my mind there is no reason to justify spending $75 on a nano tank, when it is just the glass. It's just not worth it-you can make many other tanks look just as nice for a lot less money.
However, I like to snag fancy tanks used for better prices. A lot of the ADA tanks and Do!Aqua tanks would be perfect, but you just have to find a good deal.