TN1 is a great preservation in the truest sense of the word. It’s what you should watch if you are a fan who wants to see exactly what it looked like in 1977, whether you were around back then or not.
Despecialized is better for all other purposes though. If you’re watching or showing someone the series for the first time, especially kids, that’s what you should watch. It’s probably closer to the original film negatives due to being sourced mostly from the Blu-Ray and has a lot more clarity and detail, while TN1 is an old print several generations removed from the original. That means it’s closer to what was actually seen by the public in 77, but it’s not the way it was originally intended to look.
For me, Despecialized is my “main version” now and I don’t see that changing unless we get an official release, but I’m still glad I have TN1 and it was a great watch.