I'm new here but I can tell you what I choose (and what I found by looking all over the forum and around...)
I just received my DS110j and 2TB drive this morning. Formatting right now, as I'm writing.
Why are you thinking about 7200rpm drive ??
I learnt it few weeks ago : there are 5900 rpm drives.
Which seem to be the best choices for our NAS.
Like the one I chose : Seagate ST2000DL003
It's 2TB, Green drive. (meaning from the specifications : lower rotation speed, lower consumption, less noise, less consumption, but same speed for data)
A good review : http://www.storagereview.com/seagate_barracuda_green_2tb_review_st2000dl003
You also have the other from WD and Samsung.