I buy whatever is cheapest.
I know it's a toss up no matter what or when you buy hard drives, so the only thing I have left to guage is price, capacity, and speed (RPM) depending on the intended use.
About a year ago I took a gamble on an SSD for my primary workstation. I bought an ADATA SX900 64GB drive. I had never heard of the brand before. It was ~$120 at the time, and the cheapest for that capacity. I've been looking at getting a 128GB (or so) SSD for my laptop. Prices right now look like I will be getting another ADATA... but I am holding out for Black Friday/Cyber Monday deals to decide.
Oddly enough, over the past 10 years, I've never had a hard drive die in any of my computers while in use. I have a stack of 4 or 5 drives, ranging in capacity from 100GB to 500GB, 3 different different brands, that I'm not using right now. A while back, I plugged one in just to see if it still worked and it didn't. I recently found out it was the hotswap bay that quit working, so as far as I know it still works.
Conversely, I have some servers in a datacenter. Had a drive fail on reboot after a kernel upgrade the other night. Sent a ticket to the DC and they plugged a new one in. Good to go again. In case you're wondering, it has 4x600GB SAS drives in RAID-10.
TL;DR: Buy whatever is cheapest, the odds are always the same.