Back when the PSP was current, large MicroSD cards were expensive so it made sense to get a dual adapter and use two smaller MicroSDs instead. Now it makes less sense since 128 and 200 GB cards are so cheap, and by using a single card it makes it simple to plug the MicroSD into a reader for transferring files, and 128 GB is plenty of space for PSP games anyway. But do keep in mind, you can use the dual slot adapters with a single card, you don't have to use both slots. So it still makes sense get a dual slot adapter, so you have more options if you decide you need more space later down the line, you can just add another card of equal size than switching out the card for a larger one.