HDD brand

It seems like they all have their own quality control issues at some time or another. I prefer western digital and samsung, but if the price is right I may pick up the occasional seagate or hitachi.

WD or Seagate HDD's for me

OCZ, Samsung, Crucial or Intel for SSD's

Hard to be objective when answering this question. Typically it's not even so much the brand that matters, but the specific model. Also, what you're wanting to get out of the HDD is quite relevant. For example, a system drive (C: drive) vs a data drive (i.e. dedicated for movies). I currently have 5 drives in my case, an SSD (for system) and various drives for data (movies, music, documents...). The HDDs are Samsung and WD. WD including black, blue and green.

Anyways, to answer your question, don't get hung up on brand, instead narrow it down to model and then price. You really can't go wrong with any of the brands out there.