I'm a user of such products, let me put in my 2 cts...
Bounce card, I use this in situations where there is a high ceiling or no ceiling for me to bounce on, flash is normally set at 60 degrees or 90 degrees depending on the range of me to the subjects. This will allow a large amount of light to be bounced from the ceiling if there is any and via the bounce card to give a catchlight effect.
I'd use the magiclight where there is a good bounce ceiling height and this diffuses the throw of the light when directed upwards and around. Imagine the light in a \ / shape. This gives a well diffused light against the subject and also allows the light to be directed upwards at the ceiling to be bounced back to illuminate the area.
Thus, both of these products works hand in hand for me... different situations, different usage.