Fury and Arms both offer certain specific buffs.
Arms warriors bring enhanced Bleed Damage and Enhanced Physical Damage (Trauma and Blood Frenzy), while Fury Warriors bring Rampage (5% Melee/Ranged Crit).
Rogues/Ferals have identical buffs so it's really a matter of what your raid group is missing.
As for getting for Armor Pen, the thing about Armor Pen is, the SEP of it goes up the more you have of it, gemming it is silly if you have virtually none to begin with. If you really want to see whether or not you should gem for it, run a spreadsheet (Landsoul's).
Edit: On a second note, after looking at your Armory your ARP is rather low, what you should do is continue to gem STR, but start grabbing ARP pieces where-ever you can.