Well, the blues are both tactile and clicky, whereas the reds are linear.
So, the only sound of the reds is the bottoming out sound, and their range of movement is smooth, with no bump.
The best thing to do is to find somewhere local where you can try them out, PCWorld may have a Corsair board out on display you could try and see how you like them.
The reds feel very light, and took me a while to get used to coming from blues, but once I did I loved them. (I've since gone back to blues, and now am using blacks
)