iPhone 5c has most storage, Galaxy S4 the least
Based on this article, the iPhone 5c took the crown with the most storage available from start, compared to other current-gen phones, while Samsung has the least.
This can probably be attributed to the size of TouchWiz. Then again, you can always increase storage with a microSD card. Still, as far as I know, it isn't going to be as fast as flash storage.
But most importantly, it speaks volumes on the benefits of unmodified Android.