If you can afford purples, go purple. These are nothing more than rebranded reds (NAS drives designed for constant uptime) with different firmware to handle multiple recording streams simultaneously. They are excellent drives. As far as longevity goes, they're too new for any of us to tell. They've only been on the market 2 years or so. I personally have a lot of 8 of them in service at a few different locations in Hikvision NVRs and no issues whatsoever.
Avoid Seagate like the plague - they simply do not last. The higher the capacity, the shorter the life. I toss so many Seagates it's not funny. Back in the day they used to be good and WD used to have a higher failure rate, lately they've traded places by comparison.
HGST is short for Hitachi a Global Storage Technologies. Hitachi is a decent brand to buy as well. I've had fairly good luck with them with regular computers (never put one in an NVR). However WD bought them out a few years ago, so if you see a drive branded as Hitachi, it's truly a hitachi drive. If it says HGST, it's Western Digital. While I haven't had an HGST drive come back to me dead YET, so far so good.
Another aside on the rebrand note, Samsung, who once manufacturered Rock solid drives, sold their HDD division to none other than Seagate. As such, any Samsung branded drive that has a model number starting with ST (Seagate technologies) is junk. If it's an older one starting with HD, it's good. The common name for them is SpinPoint, but Seagate still carries this name which is misleading to anyone hunting for a Samsung drive because they're just using the name which I think is wrong. Just absorb Samsung's HDD op and be done with it. Don't mislead customers. I fell victim to this once and never again. Died 8 months into service, replacement died 6 months later.
I am also a daredevil and deploy greens in my NVRs on occasion, which is explicitly frowned upon because greens have a slower spindle. (Variable speed between 5400-5900 RPM, while purples reds and blacks are solid 7200). You *may* experience degraded performance with greens because of the slower speed. With that being said, the only time they have every hiccuped is if I open playback on a full matrix of IP cams and play them back at some ridiculously fast speed. Playback of less cams or less image quality they do fine. I'm not trying to justify the usage of green drives, because someone here will shoot me down in an instant, I'm just giving an honest perspective of my drive variations. While I can manage to make them work, I would never recommend them for a beginner or someone not familiar with recording and storage technologies.
Sent from my iPhone using Tapatalk