IBM XIV Gen3 or Stornext SAN?

Quantum Stornext seems to be mainstream and widely used for video production storage but as the business I work for already own an IBM XIV Gen3 I could easily use it over iSCSI with our Macs, why would I choose to build an other SAN with a Stornext filesystem for our video needs?

We only use Macs with OSX 10.7 editing 1080p ProRes 422 file in FCPX. We also plan to sometimes use it for live ingest and editing a maximum of 4 SD feeds with Telestream Pipeline hardware. Our space need are low (10-15TB / year) because we already have an LTO-5 tape library for archiving content...

We need a storage system with maximum reliability and expandability avoiding compatibility and performances issues. The XIV is and will be use for other storage needs but it's not an issue to add 1 or 2 extra storage units to boost performances and storage space.

It's just about to get the best video storage system. What are your thoughts ?

Thank you,

Eric