8472 could've carried out its extermination plans on any number of non-Borg worlds conveniently to hand, too. I would say that these two imaginary events cancel each other out, except that on screen the Borg can't beat 8472. That's the Borg motivation for their part in the story. What happened to the hypothetical Borg ability to slaughter 8472?
It's like Equinox, the script is determined to portray Chakotay as somehow equally right, or at least that it would be reasonable to think so. But the real logic of the fictional situation (not to bother with real world parallels!) says Chakotay was wrong.