From: ExThaNemesis | #174
Like I said, canonically stated that the fusion is made stronger by the fact that they're rivals fused by the potara.
Yeah, I forgot about this.
Potara rings have two advantages. It's permanent, and it's Goku and Vegeta, while fusion dance is a totally separate entity, a completely new person that's a combination of Goku and Vegeta, but not Goku and Vegeta themselves. If that makes any sense.
There is a reason the Supreme Kai retained his personality when fusing with Kibito.
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