Wow! It makes a big difference in the way you look, but you're gorgeous either way! I have really curly hair, too, but I haven't tried straightening it...yet...
My friend keeps trying to get me to let her do it, and your pics have inspired me!
You are so lucky that you can wear your hair either way! I have stick straight hair, so there's not a whole lot I can do with it. Yours looks great both ways!