Hmmm... Mouses, keyboards and cabinets more or less depend on the user and its hard to advise on which one to get. Mainly it depends on which type of grip you have. The Claw or the palm. I haven't used both of them so cant comment. But feature wise the Sidewinder is better with 4000dpi and all. But for gaming i prefer wired mouse not wireless. Sidewinder is wireless. Go to a shop and try them out and get the feel of which one is better.
Have you considered anything from Razer? I am using the Imperator and is an awesome mouse. I have large hands and they fit in nicely.