I would think the the Unisom/B6 combo would be the safer of the 2 considering its not an Rx but Zofran is a Catergory B so it's not considered unsafe. They're currently doing research on the effectiveness of Zofran vs Doxylamine/B6 on hyperemesis.
I had horrible sickness with my first 4 pregnancies but my last was much different. Not sure why. I did take Unisom & B6 when I felt sick but didn't need it as much as I anticipated with my past.
Kristi, Mommy to Josh & Nick (identical twins 6-97) Nathen (3-02), Joey (2-04), Jacob (11-05) & Aaron (12-11) I sell Tupperware!
"A person's a person, no matter how small..." Dr Seuss