I see that I blinked for a bit and disk drives went from 6 terabytes to 10 or 12 terabytes.

Yeah, its crazy how much storage capacity they have engineered onto a platter. It comes at a cost of reliability. I stopped trusting drives > 4TB. Regardless, you need RAID to justify storing anything of value on large disks. The only exception may be for backup storage.

What considerations should I consider? Is there an obvious choice for something that does not have to be high performance but should be "nice"? Or is it one of those situations where you have to really balance separate factors...

Its a bit like the Dell vs Lenovo vs blah vs blaha arguments.. They all make junk and they all make decent stuff, depending. I can only speak from my experience. First off, Maxtor had the most amazing drives in the world!! Too bad they aren't making magnificent drives anymore... NOT! We have been using WD RE4 drives for years. They are rock solid and these days they aren't expensive. They don't come in anything larger than 4TB. I was reluctant to move past this drive capacity milestone. After 4TB we started using WD gold's. They seem ok so far. Not amazing but solid enough with RAID. Personally, I don't trust them any larger than 6TB but this is not really derived from failure data... Its too early to know how reliable they are. If speed isn't a necessity we choose WD Red's. They are slow, cool and last a long time. Really, just about any drive at 5400rpm is going to outlast the faster drives. So we use these anytime we can. Its worth mentioning they are slowwww. Maybe ok for a NAS with raid10 but not ok for someones personal computer. Lastly, RAID10 is really great and the performance boost/reliability you get from this is well worth it. Just be sure to use all the same model drive and obviously use mdadm or filesystem specific raid, not "hardware" raid.