Smaug. He would win for many reasons already said, but another reason I can think of is this: Smaug is hundreds of years old, and therefore has a lot of experience. Meanwhile, Elsa has been locked up in a tower almost her entire life and was told to do anything but use her powers.
{Hold on, everyone's saying Smaug would win because fire beats ice, but heat melts ice and turns it to water, which then can extinguish fire so...it could actually be an infinite stand-off...}
{She could always call in reinforcements, or just use her powers to stay above the ground. No, she couldn't kill him very easily, but that's not the only way to win a fight.}
When bigger in size, it'll be hard to avoid him. Plus, she can't kill him. Example: An ant might be faster than you (if that's true, then that's sad), but it can't avoid you since you take up more space than you. Therefore, splat!, it's dead.
Let me explain something to the people who chose Elsa: 1. Fire melts ice 2. Smaug could crush Elsa 3. Smaug could claw Elsa to death 4. Those of you who chose Elsa obviously have never seen nor read The Hobbit
Honestly, both Smaug and Elsa fans, it's not about who's your favorite character, it's about logic on who would win. It's obviously going to be Smaug because he's bigger and his flames can melt ICE. And snow. So Smaug would win.
2. All they have is bows and arrows. He'll just step on them.
1. Fire melts ice
2. Smaug could crush Elsa
3. Smaug could claw Elsa to death
4. Those of you who chose Elsa obviously have never seen nor read The Hobbit
Tobl LISTEN to it now