Seagate had a firmware problem a few years ago and it really hurt their reputation but as far as I know they have been fine ever since. Personally I would (and have) happily buy either brand and not worry about it. For example I have 2 x 4TB WD red drives in my NAS and 2 x 4TB Seagate green drives in my PC that I back the NAS up to. They have all been fine for approx 2 years now.
The SSHD is a great option if you can only have one drive and can't afford an SSD large enough for your needs. They do boot almost as fast as an SSD. However they are largely pointless as a data disk where files are accessed too randomly for the SSD cache to really help and you might as well buy a cheaper conventional drive.
As scout_03 mentioned a separate SSD and HDD drive combo is still the better option from a performance standpoint, the SSHD is a compromise that works well in single disk PCs.