I have lived in Louisiana my whole life, and I've always considered po-boys and subs to be different things. A po-boy uses french bread.

Well there is always the argument over what a proper poboy is, and what the texture of authentic french bread is.

I thought a Poboy had fried food, not cold cuts.

Roast beef po-boys are a big deal in New Orleans.

http://www.nola.com/dining-guide/index.ssf/2012/04/rb_top_10...

The only strict requirement is the baguette style bread.