Thank you, Darius: very interesting...
Personally, I have tried creating new Windows 7, Windows 8, Ubuntu and OS X VMs, just to see how they defaulted for the virtual HDs: well, Windows 7 and 8 defaulted to SCSI for the HD and SATA for the CD/DVD, the same for Ubuntu, while OS X 10.7/10.8/10.9 had SATA for both.
Previously, I had converted two existing OS X (10.7 and 10.8) VMs to SATA, and, IIRC (at least in the 10.8 one), the SATA disk appeared as an external one (in orange).
But the most important question probably is: is a SATA virtual HD recommended for Windows 8/8.1 - or is it better to remain with SCSI...?