They are quite similar in performance *in most games*, but the 16GB is better than the 8GB if you play the latest games often as they are recently taking quite a bit more Vram than they used to take.
But, the 4060 has more features, like DLSS which XeSS can't match, and better raytracing perfromance, also a more mature platform and drivers.
Though the biggest problem in my opinion is that there are quite a few games that the A770 struggle with, since it does not have native support for DX9 or DX11, and uses a translation layer, most older games run quite poorly on it, and it is improving with each driver update, it is still not ideal.