The NAS optimization seems also to have not so extremely affected the speed, as I would have expected. CrystalDiskMark shows in all areas compared to the same size (but significantly louder) Seagate Barracuda ST2000DM001 maximum performance drop by 10-15% during read access. In contrast, the Red writing random sectors is even faster than the Barracuda, which seems to me entirely illogical and which is probably due to better cache management. In sum, it is likely the difference in performance in practice hardly feel.
At some point I'm going to install an SSD as a system disk and run the Red as large secondary backing store on.
How reliable the plate really is, I can not say yet. The old Samsung Spinpoint has certainly just 2 years endured their warranty period before SMART has reported first error. The Red has 3 year warranty, which is worth to me of about 10 Euro higher purchase price compared to the Barracuda!