Nuka-Cola is a drink that dates back to the original Fallout. In the earliest Fallout games you can get addicted to it. I will give you health and a tiny bit of radiation. With Quantum it will give you extra AP and make your pee glow, plus more radiation. Even in Fallout 3 Sierra Petrovita in Girdersade is addicted to the stuff. I bet if it was actually real in our world instead of the Fallout world, I would be addicted to it just like I am with Coca-Cola. I bet Nuka-Cola tastes like Coca-Cola. And Quantum would probably have you jumping off the walls in the equivlent of 5 Red Bulls. In Fallout 3 and New Vegas you can do a lot with of Nuka-Cola brands. Quantum and Quartz you can make Nuka-Grenades. Victory gives you 10 action points, 10 radiation and 3 hit points for 2 min (with the consequence of -1 perception.

Sunset Sarsaparilla must taste like Sarsaparilla, hence the name. The only thing you can do with it is collect Sunset Sarsaparilla Stars. You hope to get 50 stars so you can get and achievement or trophy. You also get someting else when you find the treasure. I'm not going to say because it will ruin the quest. It must be tastey. You come across more Sunset Sarsaparilla bottles than you do Nuka-Cola bottles. There is also no Nuka-Cola bottling plant in New Vegas. Sunset Sarsaparilla Billboards are every where in the game. If you find Festus the story about the soda is actually quite interesting.

So I have to ask Sunset Sarsaparilla or Nuka-Cola?

Nuka-Cola