Used the Black Versions of the HDD's for a long time always performed good and they have always been good with service for me as well. I did look into these SSD's some but haven't bought one yet either. Was thinking about it though as they are a good bit cheaper than the Samsung 960 Pros with about the same warranty. I've stayed away from the Samsung 960 EVO because of the shorter warranty. Since I pass a lot of my hardware to my wife or kids I like them to last.

I used WD Black for HDD and recommend WD to everyone. Actually I can't say that I know people who had problems with them and many of them I know use WD.
WD Black and now WD Gold are best. Some new models of WD Black and bigger capacity of WD Gold have 256MB Cache.
If someone still have data on different 500GB, 750GB, SATA II, etc and want to use one HDD I always recommend WD Black.
One normal HDD Bay have space for 3-4 3.5" HDD. That mean one HDD 4-6-10 TB, and 2x SSD SATA III are enough to normal users to keep inside PC everyday.

Everything else could be keept on WD External HDDs.
I will not use WD M.2 but I plan to buy 2TB External HDD USB 3.0 My Passport Metal Series. It's not expensive and very nice.
You can always bring some movies, music with you and play on any computer, laptop, TV. etc..

M.2 now Samsung is best.
And best to stay with 1TB options.
Eventually if ASUS Hyper 4 x16 PCI-E adapter work for RAID 0 on older chipsets as X79 and X99 than two 960 EVO 500GB.
But for now no confirmation if that work or how to force to work.

I have to concur with the statements above. I have used Western Digital HDD's for years, and I have three of the Caviar Blacks in my tower right now. In my experience they have been extremely reliable drives, and I have never had one fail in years of service with continued use. They don't even get bad sectors for that matter.......knock on wood!

However, I have not invested in their SSD's yet. I have used the Intel 2.5"FF SSD's with great success, and also am currently using 3 M.2 Samsung 960 Pro SSD's. No WD SSD's yet though, so can't comment on that in particular.