This is a question of convenience and practicality. Internal storage is great when you don't want to risk losing tiny microSD memory cards. The problem with internal storage is that it's fixed. If you buy a camera with 64GB of internal storage, it'll always have 64GB of internal storage. MicroSD cards, even if also limited to 64GB, can easily be swapped out as needed to carry on recording if a card gets full. Internal storage will need to be backed up and erased before you can continue shooting.