I think most of that, like you say, probably just came down to not wanting to produce something to unfamiliar to fans. I personally enjoyed watching them re-depict a lot of the events of ATLA. But the other would be a lot of fun, too.

I'm just exceited it looks like we'll be getting the best of both worlds! I've heard that these Avatar followup animated projects are looking more and more definitive. With any luck, maybe we'll see the rest of Aang's story and whatever happens after the events of Korra. That's my hope anyway!