I wasn't particularly fond of Nick, either. But I think there was far more depth and potential in him than there was in Tom. Tom was just a softer, cuddlier version of Nick. He was supposed to be the "bad boy" character but he had no "bad boy" qualities to him.
Nick, IMO, would have been more interesting because we'd start off not liking this guy, but there was the potential there for him to grow much more than Tom ever did. His time on Voyager
could have taught him maturity and how to accept responsibility for his actions instead of blaming other people all the time. He could have had a real character arc, whereas Tom remained mostly the same from start to finish.