But in order to bring back those two you have to murder Tuvix. By letting Tuvix live, you consider them as being lost in a transporter accident.
Which is the lesser of two evils?
1.>To consider Tuvok and Neelix lost in a transporter accident and let Tuvix live.
2.>To murder Tuvix in order to restore Neelix and Tuvok.