It's almost entirely down to personal preference. Corsair keyboards are a bit more chunky and heavy-duty, whereas Razer tend to make more stylish but more breakable stuff. Take it from someone who managed to smash their last Razer keyboard by dropping it.
For the mouse, I would recommend the M65. Love that mouse. Again, however, if I were you I'd go down to your local computer store and see if you can try them out for yourself.