Which one of these keyboards should I get? If not one of these I have a budget of £35 for a gaming keyboard.
Personally, I think the most important feature of a gaming keyboard is the ability to correctly report all the keys that were hit. On the order of 5% of three-key combinations (i.e. pushed simultaneously) do not report correctly on typical keyboards. The Sidewinder X4 doesn't suffer from this problem.
Disclaimer: I work for Microsoft, and I developed the tech in the X4...