as far as stepping into the pedals there should be relatively no difference between the red and black cleats. Due to the free float design of the red cleats (4.5 degrees from center in each direction) you will have to turn your ankle more than the black ones.
The noticeable sliding of the red cleat on the pedal can be unsettling at first but both the free float and the extra distance of the ankle turn will become second nature in time and the focus on each will diminish.
One thing you can do if you have not done so already is to reduce the release tension setting of your pedals. This will make unlcipping easier. Also try not to twist your foot when unclipping...by this I mean rotating it as if you are trying to look at the bottom of your foot. Instead think of "swinging" your heel to the outside.
When the lower leg extends at the knee it does not just hinge, it twists a little as well. With the black cleat it is more imperative to ensure the cleat is properly aligned to prevent knee problems do to this "screw-home" effect during extension of the lower leg. With the free float of the red cleat there is more room to compensate for error in cleat alignment and you are less likely to develop problems with your knees.
-j