Candies will give you a slightly larger contact area on your shoe, depending on the shoe you are using.
Here is a picture of the candy w/ road shoe
As you can see, there is no contact at all on the platform. They will do nothing for you
Here is an image of the candy with a trail shoe, has some grip, but pretty smooth
There is still a small gap between the platform and the shoe. So they will do nothing for this type of shoe
Below is a picture of the candy with a meaty mountain shoe (sorry, not the greatest)
As you can see there is contact points near the bolt and the spindle. It is only slightly more contact near the bolt of a standard C pedal, but on the spindle side you do get a decent amount of more contact. This may help distribute the pressure a little bit
If you are looking for a shoe with a platform, this isn't the way to go, go for the mallets. They give good contact on a mountain shoe and can be used with a normal shoe. Personally, the tiny amout of additional contact the Candy give, I really don't see a need for it. I think people like them because they see the small platform and perceive it as doing more than it really does.