Question about using shred to securely erase HDD

So I am thinking about using shred or dd to wipe my inteal HDD in my laptop, so I'm researching both of them heavily. And I was reading this article here about shred http://askubuntu.com/questions/17640...e-a-hard-drive
and I see the dude say "Unmount all currently mounted partitions on that device, if any." So then I went and googled how to unmount partition and I see people saying something about gparted and whatnot and I'm just getting confused, cause when I read into dd I see no one, not a single person mention anything about making sure your HDD is unmounted of any mounted partitions before you execute the wipe.

So I'm in limbo here should I use shred or dd to securely wipe my HDD. And if I choose to use shred then please explain to me in layman's terms what all the fuss is about unmounting partitions before you enter in the shred command? Is it necessary, if it is then how do I do it in the simplest way? How come no one mentions anything about unmounting partitions when it comes to dd? Thanks.

p.s. so say that my HDD is partitioned, so what if it is, why can't i just enter in "sudo shred -v /dev/sdX" and just start the wipe process and be done with it. Or **** maybe I should say **** shred and just go with dd thereby not worrying myself with partition this or partition that?