I think that both are really solid, but I’d probably pick Yub Nub over celebration song. Even though celebration song makes sense as a grand finale for the first 6 episodes, there’s something about the intimate campfire-sing-along feel of Yub Nub that just feels more impactful. Even though the entire galaxy was celebrating in that moment, really the highlight of the scene (to me) is when Luke sees the force spirits of Yoda, Anakin and Obi-Wan with him (especially given the context of the original theatrical cut, where the celebration on other planets isn’t shown). Even though the occasion is still grand, I feel like Yub Nub suits that small moment of connection between Luke and his fellow Jedi more so than celebration song.