I understand that C++ is a very fast language, but ain't C just as fast, or faster in some cases?

Then you might say that C++ has OOP, but the amount of OOP you need for most programming puzzles is not that big, and in my opinion C would be able handle that.

Here's why I am asking this: I am very interested in programming contests and competitions, and I am used to coding in C on those. However, I noticed that the vast majority of people use C++ (e.g., 17 out of 25 finalists on Google Code Jam 2011 used it, while no one used C), so I am wondering if I am at a disadvantage going with C.

Apart from the Object Orientation, what makes C++ a more suitable language for programming competitions? What are the features of the language I should learn and use to perform better on the competitions?

For background, I consider myself pretty proficient in C, but I am just starting to learn C++.