I noticed these two appear to be the two of the most popular maps, so which one is better?

They're just totally different maps.

Ragnarok is like The Island on steroids. Bigger, more diversity, wyverns/griffins, etc. Fun, but in a relaxing way. It's not hard to dominate the island by midgame.

Aberration is brutal, challenging, and has ravagers, light pets, etc. Fun, but a constant fight to survive. Even at the late game, the surface and red zones can dominate you with ease.

I know that Rag is one of the if not the most popular map, but I just don't get it. Personally, I feel the map is a little outdated and boring, I really like to do caves and bossfights, but both do exist on Rag but not in great numbers. I only ever play Rag with Primal Fear nowadays. But I have to say it's definitely a pretty map.

But Abberation, it has a really unique Playstyle, that makes up for only having a few caves and one boss. This map makes you tame creatures you never considered taming before or haven't tamed in a long time. It's really unique, how you have to work your way down into the depths through different biomes, each more dangerous than the previous.

If it was the only map I was going to play on, Ragnarok.

But if it was choosing one to add to a cluster of maps, Aberration.(Because Lost Island has kind of taken all the good bits of Rag, and added more to it.