The big problem is that OWC is asking for a massive $579.99 for the OWC Aura Pro, that's $79.99 more than Apple asks for an upgrade from 256 to 512GB. That said, keep in mind that you still have that spare 256GB SSD, although it's pretty much useless now as there's currently no other system that uses it.
Luckily OWC has come up with a solution here too, as for a limited time, they're shipping an Envoy Pro USB 3.0 enclosure to fit the spare SSD into, which means you'll have a really decent external storage solution with plenty of space. OWC claims the Envoy Pro USB 3.0 has a retail value of US$59.95, although you have to have your order in for the Aura Pro before the end of September to get the free enclosure which ships at a later date. It would've been easier to restore the MacBook Pro using the USB 3.0 enclosure, but apparently OWC is still waiting for stock to arrive.
The Aura Pro comes with a SandForce controller, whereas the default SSD from Apple uses a Samsung controller. As such there should be a performance increase when dealing with compressible data, but if you're working with incompressible data like video, then the Samsung based drives from Apple should in general take the lead. If the upgrade is worth it depends on what you're doing and if you're happy to crack your shiny new notebook open or not.
Source: OWC
