Portable is better for many reasons. Formatting to internal storage is no cure for low memory issues, SD cards are slow and will make your phone laggy, they fail frequently and as the data is encrypted there is little chance of recovery. Factory rest your device and the encryption key generated by your phone changes so you lose access. As portable storage, they are not secure.
Just remember - you can't save anything to the "SD card" - you don't have one any more. (Logically, the SD card is just "storage" - the same as internal storage.)
Just remember - you can't save anything to the "SD card" - you don't have one any more. (Logically, the SD card is just "storage" - the same as internal storage.)