I suppose a big factor, is pure chance!
I for one have IBM Drives that have been running strong for years, but I also have a few that dies within weeks, and I still cannot get them RMA'd for one reason or another )
The one make that has served me well, without a shadow of a doubt, is most definitely Seagate... So much so, that I now run ONLY seagate drives, and so far, not a single bad sector... This is not a bad thing because I have quite a number of systems, all running 24/7 and the drives dont get a minutes rest.
I now sear by seagate as opposed to swearing at IBM.