I'm not sure why anyone who wants a PS3 for FREE would not do this. Seriously, it's a completely free and safe process. It will never cost you anything.
I encourage you to choose ANY of the offers. I only used the Stamps.com offer for demonstration purposes only. I also use the mail alot. So that offer appealed to me. By all means, you should choose the offer that is right for you. There are alot of great things they are offering, and you are free to choose any of them.