i dont think SSHD are any more reliable than a normal HD 
, WD blue/black have low failure rates if that helps but all HD's have a chance of failure in the first 3 months (production line problems) then on average will last 3 years with a chance of failure every year that gets a tad bigger.
but SSHD do have the potential to be faster
got to say happy to see you have an external backup +1 for that drive failure can happen any time and data lose can be bad
, WD blue/black have low failure rates if that helps but all HD's have a chance of failure in the first 3 months (production line problems) then on average will last 3 years with a chance of failure every year that gets a tad bigger.but SSHD do have the potential to be faster
got to say happy to see you have an external backup
+1 for that drive failure can happen any time and data lose can be bad