I can't believe so many people can't see that the cases of Quinn and Tuvix are both cases of the rights of the individual vs the will of the majority with her verdict in both cases resulting in the death of the individual.
In the case of Quinn, Janeway decides the rights of the individual is more important than the will and laws of the state.
In the case of Tuvix, she decides the good of whole is more important than the pursuit of life and liberty for the individual. Plus, it seems her decision was more of an emotional one than a rational one. When Kes came to her in tears saying she wanted Neelix back, Janeway couldn't refuse.