The reasons presented so far are perfectly adequate, but I wanted to point out one other thing as well.
at the battle of sector 001 the USS Defiant along with the federation fleet engaged the Borg cube. in that battle numerous ships were destroyed with several ships being destroyed very quickly by the Borg. the Defiant however survived multiple hits from the borg and was eventually left adrift. tho the ship sustained heavy damage it is still puzzling how the Defiant was able to withstand hits that destroyed other vessels so easily.
How do we know that? What reasons are there to assume that the ships that went down were destroyed "easily"? For all we know, every ship in that battle that was destroyed on-screen had
already been beaten to crap, and the blow that destroys the ship is, quite literally, the finishing blow. Some of those ships could have been fighting the cube for hours; it's never made clear just how much time goes by from the moment Picard decides to head for Earth to the Ent-E's arrival at the battle, but given that they were near the Neutral Zone, it had to be quite some time.