Which 2nd hard drive for my MBP 2011?
I have the Seagate in my 2010 15" MBP and I have had 0 problems with it.  It's dead silent and there is no vibration.  My battery life stayed pretty much the same after the upgrade, but since you are looking at dual hard drives (I'm assuming you removed your optical drive) I would expect to see a slight drop in your battery life.

I would stick with the 7200rpm drives over the 5400rpm myself.