SSD have a built in failure, There is a limited number of writes that a NAND cell can sustain. HDDs do not have this inherant failure as the magnetic domain can have its polarity reverse as long as it remains intact.
An SSD uses an electrical grid axis (X,Y,Z being the charge) this axis is not mecahanically controlled. HDDs also X,Y axis (Z being the magnectic polarity), But must be access by mechanical means. mechanically. For HDDs the ability to maintain the sector alignment increase is more difficault as the domains become smaller.
But to the question which was do Larger HDDs have a higher failure rate. I've not seen a report that shows this, But if you look at new egg, you could get the impression that as the size goes up from...