Which version should I get? HELP! 10 points!?

I have a Dell, but I'm getting bored. I love to make videos for youtube and experiment with different video effects, and for my Dell Inspiron 600 m, when I make a video for youtube, I have to use a free video converter, and then import my videos onto the free Pinnacle Video Spin that will go slow and freeze. And that's why I want a Mac laptop. My only requirements are that it's a laptop, decent price. has a webcam to take pictures and videos for Imovie and Photo booth, and that I can have the software of Microsoft word and itunes, which version of the Mac should I get? ANd one that will be fast and won't need a lot of software and won't get a lot of viruses and spyware or freeze.