ATLA season 3 would be the best but after that I'd definitely rank LOK season 4 above ATLA season 2. Also I will admit, if I put all 3 ATLA seasons and all 4 LOK season together and had to rank them all, some LOK seasons would be higher than ATLA. I treated Korra more as a spin-off rather than a sequel since I knew it would center on an all new cast with sprinkles of the original ATLA cast, which is what I believe it was to be the original intention for writers.
Season 3 and 4 were great but season 2 was meh. I thought season 1 was alright, a little slow but alright since it was world building. People don't like Korra as a protagonist either. As someone who watched it when during its original run, I know some of my friends were expecting to see something along the lines of a direct sequel just without Aang. The Minecraft server IP is, more info here. These avatar themed subreddits are fully or partially run by moderators of /r/TheLastAirbender They build towards LoK and answer some questions left at the end of ATLA. There are several main comics which take place shortly after ATLA.