worst fate

A very interesting point you've brought up - paralleling these two foes as the ultimate human enemy... In both cases, you would under control by the force that makes you do hideous things while your suppressed consciousness looks on hopelessly and it would be hard to return to the life you once had. I'd say being made host for a Goa'uld symbiont would be much worse as you individually are responsible for the inhumanity and pure evil the symbiont would make you do. As a Borg, you are part of a great collective, so you are dispensable and won't individually make a great impact - and I believe by the time of Star Trek: Voyager, there are ways to disconnect individuals from the collective and try to reintegrate them back into society (where Seven of Nine comes in).