On the Portable, the Floppy Emu can function like an external hard disk, connected to your external floppy port. It's not a SCSI device, however. You could use it simultaneously with a SCSI drive, like a SCSI2SD or a real hard disk - then you'd have two hard disks. I'd say the best path depends on what you want to do with it. If you want something internal that's the most similar to having a real hard disk, then SCSI2SD is probably the best solution for you. But if you also want the option to emulate floppy disks, or you want to download a lot of Mac software disk images from the internet to an SD card, then I'd recommend the Floppy Emu. Of course, I am biased.