The only difference is the width. The Allplay is 8mm wider than the Whipit. For this reason the Allplay is still good on firm/groomed snow but it's extra width makes it perform just as well in up to 10" (25cm) of powder so it's more versatile on a wider variety of terrain. More Allplay info...

The Whipit is better on firm snow because it is narrower and quicker but it has less float in the powder. If you ski mostly firm snow or park then you'll gain quickness and a very nimble feeling. More Whipit info...