Hey Mike,
Yep, opinions are like a lot of things, and the thing to keep in mind is that there are lots of ways to do things, none of which are wrong. It comes down to, personal preference, environment, even bad experiences form how we decide things. I even started writing a Medium article about storage bits, but need to keep working on it, as it's still a draft even though it's live, IMHO.
For context, I've got around 25tb of mostly photos, and my primary work machine is a Macbook Pro that I use for my day job as well. I have a 40tb Synology as my spinning primary storage, setup in RAID6 and have added the SSD caching feature. My process is to import from cards to either the internal drive, or a USB-C enclosed SSD drive as my working space. If I need the cards back in action asap, I'll immediately make a second copy from card to the NAS, otherwise I'll copy the processed files from the SSD's to the NAS before the cards go out. My backups happen directly from the NAS to external USB3 drives, be it I'm home or not.
Comparing workflows, we both work off DAS first, but I'm quick to move off to NAS for long term storage, while you rely on the DAS RAID 10 for you long term primary storage. If I need to work on something that has already been moved to the NAS, I'll copy it back to the SSD and do something else while the copy happens. I tend to only use single spinning drives for backups. I trade off having a large 'working' drive for a much faster, but smaller & portable SSD.
You've meet Murphy I see
Yea, he shows up at the worst of times. I wouldn't consider a SAS based setup unless you're dealing with Terabytes of rewritten info constantly, and it's part of a larger NAS/SAN setup - the price point of SSDs, even doing mirrored drives, is much cheaper & faster than anything that spins. The thing about SAS 10/15k drives is that they don't wear out after so many write cycles like SSD's do. But at what point is the trade off of replacing the SSD every 6-18 months worth it? Time is money, and I'd rather not sit around waiting.
NAS's have actually been pretty good to me over the years. There are some major advantages on the technical level, things like ZFS that you wouldn't get on a Mac or PC, but there can be some challenges for those who aren't technically inclined. I do IT for a living, so some of my selections aren't of the 'best for your average user', but I moved from a NAS4free ZFS setup to a Synology just because I didn't want to fuss with it and need to grow the amount of storage I had available.
-Joe