At the time I was doing my shopping research, LaCie had the only ~$1000 solution capable of +750MB/sec, period. For day to day work under pressure, not for redundancy or data safety.
Of course, I keep a separated backup, what of course doesn't need to be as fast as the main fast storage. That's also why I don't need RAID5, 10, 6 or any other. RAID0 is the fastest.
NAS, personal cloud, FTP, mail, sure are pretty, but that's not my point here, I need a fast, very fast storage for day to day use. All that NAS features are complementary, I would not mix them here.
And you can have some of these features and some more just upgrading the free Mavericks to Server, for ~$20. But again, that's not our topic here.
1. What are you doing that requires that much speed? Not even the fastest SATAIII SSD's are that fast, only PCIe SSD's (which are set up as RAID0) and fast RAID's can achieve those speeds. I recommend a quality NAS for archive purposes, and anywhere the speed of say a WD Black is sufficient a good NAS can easily match those speeds. This makes them useful for mos peoples image processing needs. Video is a different animal.
2. Agreed. The op wasn't clear if he was looking for a work or archive drive.
3. Features are added value. When choosing storage, if you're sitting on the fence between two solutions it could be beneficial to consider features.
4. You could, but IMO there are many benefits to keeping your workstation separate from server duties. Security being the most important reason followed by the extra resource drain on the workstation, the workstation might not be up 24/7 or you might not want to leave it on 24/7 while on vacation, and then there's the ability to remotely manage your RAID with a good NAS that you wouldn't otherwise have.
Bottom line, if the OP is processing images and looking for a storage or work drive, a NAS on a wired Gigalan (not wifi) a NAS should be considered. If his needs are for a super fast work drive for any reason (though for images it is probably overkill, even large multilayer tiffs take less than a second to load from my NAS) then a TB device starts to make sense. Or if he just doesn't want to manage a NAS,.. It's all about needs and for most of us.. value.