I believe PX-712A (PATA) may have a temporary advantage over PX-712SA (SATA), not in terms of hardware, but in terms of burning software support.
On many modern motherboards that support both SATA and PATA interfaces, the SATA port resources may be “non-legacy” mode, mainly to allow the PATA ports to assume the usual legacy resources, such as IRQ 14 & I/O ports 1F0-1F7 for primary IDE, and IRQ 15 & I/O ports 170-177 for secondary IDE. With a PX-712SA connected to a SATA port with non-legacy (native) resources, some burning software may not be able to detect the Plextor properly.
This means some burning software programs are in potential need of new enhanced versions that know how to scan for CD/DVD writers on SATA ports (in both native and legacy modes) as well as the usual PATA/IDE ports. Once these programs are able to provide proper support for SATA-based writers, then both interfaces should work equally well.
I don’t have access to a PX-712SA so I cannot assess the true compatibility of this drive with current burning software such as Nero, etc. I already own a PX-712A and a PX-708A, and don’t intend to purchase a PX-712SA purely for research purposes.