The Gemara on the first Mishnah in the fifth chapter has a disagreement between Rav Yehuda and Rav Aina whether it's Simchat Beis "Hashoeva" or "Hachashoova." and Rav Nachman seems to say that both answers are equally good even though one gets his source from a Pasuk while the other doesn’t. How can both answers be equal?

ב"ה Shalom The issue in discussion in the Gemara (Sukka 50b) is not about Halacha for which each of the Amoraim are quoting a source to prove their side. The issue is how each one referred to the drawing of the water. One refers to the aspect of the drawing of the water as can be inferred from the word "Ushe'avtem Mayim" and therefore finds the word "shoeva" suitable, while the other refers to the importance of the water drawing since the "shitin" which receive the water are existent since creation, and therefore chose the "Chashuva" which means important. Therefore they are equally entitled to their perspective. All the best