If the Borg cube was up against the USS Saratoga, assimilating first officer Sisko might have made a difference there.
Any particular reason why the Borg would want the first officer of such a small ship?
When Picard was taken, the Borg took the time to explain to him why - he was the captain of the most powerful ship Starfleet had, and thus, he would be their spokesman for the assimilation of humanity.
That never made any sense to me. Why wouldn't the Borg just come in and assimilate the crap out of everyone? Why did they need a spokesman? What did the Borg plan to speak about? Maybe try to convince people that being assimilated really wasn't so bad after all?