1. I assume this is a laptop.... if not use 3.5" 7200 rpm. The Seagate 2 TB SSHD is more than 50% faster in gaming than the WD Black.
2. What is the usage ? SSHDs are great for data storage. In an office, you tend to use the same files day to do day... so if I am designing say a treatment facility, I am opening the same AutoCAD file(s) day to day, I am opening the same word processing files day to day. Invariably I will get 'callbacks' to look at 2 or 3 other projects over the course of several weeks. Now all these files will be located in the SSD portion of the drive which means they load faster, The same is true for gaming, When playing say Far Cry 3, the day to day files are on the fast portion of the drive ... when you move oin to FC4, after a few loads, FC3 files get moved off and FC4 gets moved on.
3. Boot Times:
Seagate 2 TB Barracuda = 21.2 sec
Seagate 2 TB SSHD = 16.5 sec
Samsing Pro SSD = 15.6 sec
4. We typically install (1) SSD and (1) SSHD as a minimum... (2) of each is not unusual. On Budget systems, if it comes down to using just 1 storage device it's a SSHD... proverbial "no brainer" when storage budget is $85
5. Have not installed a HD in over 7 years other than for test purposes. In that time, installed dozens of SSHDs ... 0 failures to date. Over same period (3) SSDs have failed, one of those was a warranty replacement that also failed. We have had no SSD failures with the Samsung 850 Pro or newer.
6. In user testing (5 users) whereby system could boot from HD, SSD and SSHD .... boot drive was changed w/o user know;ledge each day over a 6 week period... one user thought system might have booted slower on one occasion. No one noticed any difference between SSD and SSHD. Test was repeated w/ two identical laptops... SSD + 7200 rpm HD and 7200 rpm SSHD) .... no one could tell the difference.
7. A 2 TB SSD is in the neighborhood of $300 ... for a cheap one ... one ya'd want ... $500.... the best $1000
8. My PC has twin 250 GB SSDs and twin 2 3.5" TB SSHDs. All the other boxes here one of each. Our lappies all have 7200 rpm SSHDs. The distributor who custom builds our laptops, tells me that there's "no such thing" as a 5400 rpm 2.5" SSHD unless ya want to buy out existing stock on these. As that product iis at least 6 years old, I expect the current FireCUDA 5400 rpm laptop drives are just as fast as the old 7200s due to increases ina ereal density over that time span.
https://www.amazon.com/Seagate-Momentus-7200RPM-Hybrid-ST750LX003/dp/B00691WMJG
9. Yes, you can run tests like moving 500 GB of files and "prove" how much faster the SSD is. I do that like once every couple of years. But when i do, I use my free backup program to make a mirror of one drive to another at 3 am in the morning. When Im sleeping, I don't really care how fast it gets done. You can even run an MS office Script of 1134 actions and the SSD will win easily.... but in the real world, key strokes are needed between each action which renders the SSDs speed advantage irrelevant. Its like when I commuted tot he office i rush hour traffic, I never once said "OH crap, Im late ... I better take the Porsche" .. whether I took the Porsche or I took the SUV, when traffic is stop and go and it takes 45 minutes to go 17 miles, having a faster car doesn't help in any way. As to the HD or SSHD choice, yes... if ya stare at the screen, you can pick up the speed difference. But if you work like a normal person and push the on button on ya PC when you arrive at ya desk, who cares about boot time ? I'm reading / listening my phone messages, returning the calls, or grabbing coffee ... by the time I get dome with that, after 15 minutes, the fact that the machine was 0.9 seconds faster to boot doesn't mean a whole helluva lot.