The Pokebeach translation is the correct one.
Generally what happens when we have a mistake on Beach is that I read the card correctly, but type the wrong word in the spoiler. I discover the error either upon re-reading the spoiler or when somebody proposes a strategy that isn't feasible on our boards, and we get the mistakes ironed out within a day of posting. The problem with something like Sunflora is that the typo makes sense in context, and when people read things, their brains automatically fill in the information they "expect" to see. So, even after reading the card several times, the error is so innocuous that it slips under the radar.
I'm guessing this is what happened to PUI when they translated Onix: Someone misconstrued the first "this Pokemon" as "your Pokemon", then the second "this Pokemon" became a reference back to "your Pokemon". Every time they read the card after that, it seemed like that was what it was supposed to say. So I can understand where the error came from, and I empathize. My real question is how the card made it past playtesters and QC. If I'd proposed a Basic Pokemon with a stackable body that abuses Rain Dance, even Water Pokemon Master--who SWEARS by my translations, would've sent me back to recheck the source!