The Borg stopped making sense as an enemy when we saw just how many cubes they actually had, not to mention their ability to time travel whenever they wanted like in First Contact.
I had never actually thought of that, but it makes a lot of sense.
The Borg are going to be very practical in their approach, if at first something doesn't succeed, adjust tactics and try again--resistance is futile after all. If in the case of humanity, it would make more sense for them to--starting in the DQ--send a ship back to lets say 2012, have them transwarp to Earth and then assimilate us all. We'd never stand a chance, and the Borg would have successfully assimilated humanity, thus saving themselves two cubes in the process.
I think I'll definately be sticking with the Dominion on this one.
Now all out war between the Dominion and the Borg, who would win?