I've had both. Only ever had a WD go and contacted them for an RMA. I was pretty disappointed with their customer service. They sent me a new drive using the slowest shipping possible. Came from Ontario (I live in BC) and took 9 days. It was a backup drive, but still, they didn't know that. You'd expect them to be a little more concerned with your uptime than that.
I had to ship the old unit back at my expense. Cost me about $12 CAD, which is a substantial charge in comparison for what some drives retail for (they were also offering an upgrade program where I could swap the drive for higher capacity for $49.99 CAD, it was tempting.
This coming from the experiences I've had with Apple repair, where they overnighted batteries to me, took back my headphones, etc. and I didn't have to pay a dime. A DHL guy would show up, I would get the new product, and throw the old product in the given envelope and call a delivery guy for pick up... maybe they've spoiled me.
In any case, I am far more hesitant to deal with WD (and I've always traditionally relied on them over any other manufacturer for HDs). I've never dealt with Samsung so they could be just as bad (or worse).