Question about weapon types for Rogues

[DinoTriz]

I just got my Rogue to 13 and got Dual Wield. I was curious what was status quo or popular with Rogues regarding which weapon types they use?

I understand that you HAVE to have a Piercing weapon in the main hand in order to Backstab, but what does everyone use in Secondary? What is best? Slashing > Piercing?

I have a Slashing weapon in my offhand atm, but it was all I had available. Thanks guys!