Kiwi has been tested on iPad, iPad2. iPad 3 and all levels of storage (16, 32, 64 GB). Kiwi works on all models.  Since Kiwi is an internet based program, none of your Kiwi data are saved onto the iPad itself.  Therefore, there are no Kiwi benefits when using a 16GB or a 64GB iPad.  The option to choose a larger storage device relates to your own personal use (music, viedos, games).